Class 8 Science and Maths Solutions Free

Chapter 1 Crop Production and Management

Q: What is crop production?

A: Crop production is the process of growing crops for human use.

Q: What are the essential inputs required for crop production? A: The essential inputs required for crop production are seeds, water, nutrients, sunlight, and proper temperature.

Q: Define the term 'crop rotation.'

A: Crop rotation refers to the practice of growing different crops on the same land in a pre-planned sequence.

Q: Name the two types of crops based on the seasons.

A: The two types of crops based on the seasons are kharif crops and rabi crops.

Q: Give examples of kharif crops.

A: Examples of kharif crops include paddy, maize, cotton, and soybean.

Q: Provide examples of rabi crops.

A: Examples of rabi crops are wheat, barley, peas, and mustard.

Q: What are the major sources of irrigation in India?

A: The major sources of irrigation in India are wells, tube wells, canals, and tanks.

Q: Define the term 'weeding.'

A: Weeding is the process of removing unwanted plants or weeds from the cultivated crops.

Q: Why is plowing an essential step in crop production?

A: Plowing helps in loosening the soil and turning it upside down, making it suitable for sowing seeds.

Q: Name the two groups of fertilizers.

A: The two groups of fertilizers are organic fertilizers and inorganic fertilizers.

Q: Explain the term 'manure' and its importance.

A: Manure is organic matter obtained from decomposed plants and animal waste. It helps in increasing soil fertility and improving crop yield.

Q: What do you understand by the term 'harvesting'?

A: Harvesting refers to the process of cutting and gathering mature crops from the field.

Q: How are cereals different from pulses?

A: Cereals are grass-like plants grown for their edible seeds, whereas pulses are leguminous crops that produce seeds inside pods.

Q: Name the two types of fertilizers based on the nutrients they provide.

A: The two types of fertilizers based on the nutrients they provide are nitrogenous fertilizers and phosphatic fertilizers.

Q: What is the method of sowing seeds in which we put seeds one by one in the soil?

A: The method of sowing seeds one by one in the soil is called broadcasting.

Q: Define the term 'herbicides.'

A: Herbicides are chemicals used to kill or control unwanted plants or weeds in the fields.

Q: What is threshing?

A: Threshing is the process of separating the grains from the harvested crop.

Q: Explain how storing grains after harvesting is important.

A: Storing grains after harvesting prevents them from getting spoiled by pests, insects, and fungi. It ensures food availability even during non-growing seasons.

Q: What are the advantages of using manure over chemical fertilizers?

A: Manure improves soil fertility for a more extended period, retains moisture, and does not harm the environment. It is cost-effective compared to chemical fertilizers.

Q: Give examples of oilseed crops.

A: Examples of oilseed crops are groundnut, mustard, sesame, and sunflower.

Q: Describe the process of winnowing and its purpose.

A: Winnowing is the method of separating chaff from grain by tossing it in the air. The heavier grains fall vertically, whereas the lighter chaff gets blown away. It helps in obtaining clean grains.

Q: What are the steps involved in the preparation of the soil?

A: The steps involved in preparing the soil are plowing, leveling, and adding manure or fertilizers.

Q: Explain the term 'irrigation.'

A: Irrigation is the process of supplying water to crops at regular intervals when there is a scarcity of rainfall.

Q: Name two types of irrigation channels used in farming.

A: Two types of irrigation channels are canals and drip irrigation systems.

Q: What do you mean by 'harvesting index'?

A: Harvesting index refers to the total crop weight (edible parts) in relation to the total plant weight (including roots, stems, etc.).

Q: Mention two methods of irrigation used in hilly areas.

A: The two methods of irrigation used in hilly areas are terracing and building of bunds.

Q: Define the term 'manuring.'

A: Manuring refers to the process of adding organic or inorganic materials to the soil to increase its fertility.

Q: State the difference between organic manure and inorganic manure.

A: Organic manure is derived from natural sources (plants, animals) and improves soil structure, while inorganic manure is artificially manufactured and provides specific nutrients to the soil.

Q: Why is plowing done before sowing seeds?

A: Plowing loosens the soil, increases aeration, and helps in the proper mixing of organic matter and fertilizers, thus preparing an ideal seedbed.

Q: What is the biggest advantage of multiple cropping?

A: Multiple cropping allows farmers to grow more than one crop on the same piece of land, thus maximizing the yield and reducing the risk of crop failure.

Q: How does crop rotation benefit farmers?

A: Crop rotation helps in preventing the depletion of specific nutrients from the soil, controls pests and diseases, and maintains soil fertility.

Q: What is 'vermicomposting'?

A: Vermicomposting is a process in which earthworms are used to convert organic waste into nutrient-rich compost.

Q: Explain the term 'sowing.'

A: Sowing refers to the process of placing seeds or seedlings in the soil for their growth and development into mature plants.

Q: Name two types of harvesting machines.

A: Two types of harvesting machines are combine harvesters and threshers. 35. Q: What is the role of nitrogen-fixing bacteria in agriculture? A: Nitrogen-fixing bacteria convert nitrogen from the air into a form that plants can utilize. This process helps in naturally enriching the soil with nitrogen.

Q: Why is it essential to protect crops from pests and diseases?

A: Pests and diseases can damage crops, reduce yield, and affect food production. Protecting crops from pests and diseases ensures a healthy harvest.

Q: Define 'storage pests.'

A: Storage pests are insects or organisms that infest and damage stored grains or harvested crops.

Q: What are the precautions a farmer should take while using fertilizers and pesticides?

A: Farmers should follow the recommended dosage, wear protective clothing, avoid overuse, read product labels carefully, and refrain from using excessive chemicals.

Q: What is the role of sunlight in the process of photosynthesis?

A: Sunlight is essential for photosynthesis, the process by which plants convert carbon dioxide and water into glucose (food) with the help of chlorophyll.

Q: Name the equipment used for sowing seeds.

A: Equipment used for sowing seeds includes seed drills, broadcasting equipment, and transplanter machines.

Q: Why is it necessary to grade harvested crops?

A: Grading helps in sorting out the harvested crops based on quality, size, and appearance. It ensures uniformity and helps in fetching better prices in the market.

Q: What is the ideal time for harvesting most crops?

A: The ideal time for harvesting most crops is when they reach maturity, which can be identified by specific changes in color or texture.

Q: Explain the importance of soil testing before crop cultivation.

A: Soil testing helps farmers determine the nutrient content of the soil, its pH level, and the presence of any harmful substances. It helps in making informed decisions regarding the application of fertilizers.

Q: What are the advantages of using genetically modified crops?

A: Genetically modified crops offer increased resistance to pests and diseases, improved productivity, enhanced nutritional value, and better adaptation to environmental conditions.

Q: How can pests and diseases be controlled naturally?

A: Pests and diseases can be controlled naturally by using biopesticides, crop rotation, intercropping, biological control agents, and maintaining proper crop hygiene.

Q: What is the purpose of drying harvested grains before storage?

A: Drying harvested grains helps in reducing moisture content, preventing spoilage, and inhibiting the growth of mold or fungi.

Q: What measures can farmers take to conserve water during irrigation?

A: Farmers can conserve water during irrigation by adopting drip irrigation systems, mulching, avoiding over-irrigation, and using methods like sprinklers or furrows.

Q: How can pests and diseases be identified in crops?

A: Pests and diseases can be identified by observing symptoms such as wilting leaves, discoloration, pest droppings, presence of eggs or larvae, distorted growth, or abnormal plant behavior.

Q: Explain a few methods of weed control in agricultural fields.

A: Methods of weed control include manual weeding, use of herbicides, mulching, crop rotation, and intercropping.

Q: Discuss the importance of post-harvest management in crop production.

A: Post-harvest management ensures proper storage, transportation, and processing of harvested crops to prevent spoilage, maintain quality, and maximize their economic value.

Chapter 2 Microorganisms: Friend and Foe

Question: Define microorganisms.

Solution: Microorganisms are tiny, living organisms that can only be seen under a microscope.

Question: Name the types of microorganisms.

Solution: The types of microorganisms are bacteria, fungi, protozoa, algae, and viruses.

Question: Name two beneficial uses of microorganisms in the field of medicine.

Solution: Microorganisms are used to produce antibiotics and vaccines.

Question: What is pasteurization?

Solution: Pasteurization is the process of heating milk or other liquids to a high temperature to kill harmful microorganisms.

Question: Name a disease caused by bacteria in humans.

Solution: Tuberculosis is a disease caused by bacteria in humans.

Question: What are antibiotics? Solution: Antibiotics are drugs that kill or inhibit the growth of bacteria.

Question: What causes fermentation?

Solution: Fermentation is caused by the action of microorganisms like yeast and bacteria on substances such as sugar or starch.

Question: Name a disease caused by a virus.

Solution: Influenza (commonly known as the flu) is a disease caused by a virus.

Question: How are microorganisms useful in sewage treatment?

Solution: Microorganisms help in the decomposition of organic matter present in sewage, thereby purifying wastewater.

Question: Name a beneficial role of fungi.

Solution: Fungi help in the decomposition of dead plants and animals.

Question: What is nitrogen fixation?

Solution: Nitrogen fixation is the process by which nitrogen from the atmosphere is converted into compounds that can be used by plants.

Question: Name a nitrogen-fixing bacterium.

Solution: Rhizobium is a nitrogen-fixing bacterium. 13. Question: Name a disease caused by a protozoan. Solution: Malaria is a disease caused by a protozoan called Plasmodium.

Question: How do microorganisms spoil food?

Solution: Microorganisms spoil food by secreting enzymes that break down the food and cause it to rot.

Question: What is the greenhouse effect?

Solution: The greenhouse effect is the process by which certain gases in the atmosphere trap heat, leading to an increase in Earth's temperature.

Question: Name a microorganism used in the production of bread.

Solution: Yeast is a microorganism used in the production of bread.

Question: What is biofertilizer? Solution: Biofertilizer is a substance that contains living microorganisms that help improve soil fertility.

Question: Name a microorganism used in the production of curd.

Solution: Lactobacillus is a microorganism used in the production of curd.

Question: How are microorganisms involved in nitrogen recycling?

Solution: Microorganisms decompose dead organisms and release nitrogen back into the soil, making it available to plants.

Question: Name a disease caused by a fungus in humans.

Solution: Ringworm is a disease caused by a fungus in humans.

Question: What are antibiotics produced from?

Solution: Antibiotics are often produced from microorganisms such as bacteria and fungi.

Question: Name a microorganism used in the production of alcohol.

Solution: Yeast is a microorganism used in the production of alcohol.

Question: What are pathogens?

Solution: Pathogens are microorganisms that cause diseases in humans, animals, or plants.

Question: What is the role of microorganisms in biogas production?

Solution: Microorganisms break down organic waste in biogas plants and produce biogas as a by-product.

Question: Name a microorganism used in the production of antibiotics.

Solution: Penicillium is a microorganism used in the production of antibiotics.

Question: Describe the role of microorganisms in the process of decay.

Solution: Microorganisms break down dead plants and animals, returning nutrients to the soil in a process called decay.

Question: What is a vaccine?

Solution: A vaccine is a substance that stimulates the immune system to produce immunity against a specific disease.

Question: Name a microorganism used in the production of vinegar.

Solution: Acetobacter is a microorganism used in the production of vinegar.

Question: What is the role of microorganisms in the nitrogen cycle?

Solution: Microorganisms convert nitrogen gas into forms that can be used by plants in the nitrogen cycle.

Question: Name a disease caused by a protozoan in humans.

Solution: Amoebiasis is a disease caused by a protozoan called Entamoeba histolytica in humans.

Question: What is penicillin?

Solution: Penicillin is an antibiotic produced from the Penicillium fungus.

Question: Define biocontrol.

Solution: Biocontrol is a method of pest control that involves using living organisms to control the population of pests.

Question: Name a microorganism used in the production of citric acid.

Solution: Aspergillus niger is a microorganism used in the production of citric acid.

Question: What is sewage?

Solution: Sewage refers to wastewater that contains human waste, household waste, and industrial waste.

Question: Name a microorganism used in the production of buttermilk.

Solution: Lactococcus lactis is a microorganism used in the production of buttermilk.

Question: What is nitrogen cycle?

Solution: The nitrogen cycle is a natural process where nitrogen undergoes various transformations, transferring from the atmosphere to organisms and back.

Question: Name a disease caused by a virus in humans.

Solution: COVID-19 is a disease caused by the SARS-CoV-2 virus in humans.

Question: What are decomposers?

Solution: Decomposers are microorganisms that break down dead organic matter and recycle nutrients.

Question: Name a microorganism used in the production of penicillin.

Solution: Penicillium chrysogenum is a microorganism used in the production of penicillin.

Question: What is the role of microorganisms in the soil?

Solution: Microorganisms in the soil help decompose organic matter, enhance soil fertility, and convert nutrients into forms that plants can absorb.

Question: Name a disease caused by a bacterium in plants.

Solution: Bacterial blight is a disease caused by a bacterium in plants.

Question: What is genetic engineering?

Solution: Genetic engineering is the process of manipulating an organism's genes to introduce specific traits or characteristics.

Question: Name an example of a commercially important fungus.

Solution: Aspergillus is a commercially important fungus used in the production of various enzymes and organic acids.

Question: How do microorganisms help in making curd from milk?

Solution: Lactobacillus bacteria ferment the lactose in milk and convert it into lactic acid, which curdles the milk.

Question: Name a disease caused by a virus in plants.

Solution: Tobacco mosaic disease is a disease caused by a virus in plants.

Question: What is the role of microorganisms in the production of antibiotics?

Solution: Microorganisms produce antibiotics naturally as a defense mechanism against other microorganisms.

Question: State two harmful effects of microorganisms.

Solution: Harmful microorganisms can cause diseases and spoil food.

Question: What are algal blooms?

Solution: Algal blooms are sudden and rapid increases in the population of algae in water bodies, leading to harmful effects on the ecosystem.

Question: Name a disease caused by fungi in plants.

Solution: Late blight is a disease caused by fungi in plants.

Question: How do microorganisms help in the production of compost?

Solution: Microorganisms break down organic waste during the process of composting, converting it into nutrient-rich compost.

Chapter 3 Synthetic Fibres and Plastics

Q: What are synthetic fibers?

A: Synthetic fibers are man-made fibers that are produced through chemical processes.

Q: Give some examples of synthetic fibers.

A: Examples of synthetic fibers include polyester, nylon, rayon, and acrylic.

Q: What is the chemical composition of a polyester fiber?

A: Polyester fibers are composed of long chains of ester monomers.

Q: How are synthetic fibers different from natural fibers?

A: Synthetic fibers are made by humans, while natural fibers are obtained from plants or animals.

Q: State two advantages of using synthetic fibers.

A: Synthetic fibers are usually strong and durable, and they can be produced in a variety of colors.

Q: What is the process of making nylon fibers called?

A: The process of making nylon fibers is called polymerization.

Q: Why are synthetic fibers used in making raincoats?

A: Synthetic fibers are used in making raincoats because they are waterproof.

Q: Name the synthetic fiber that resembles silk.

A: Rayon is the synthetic fiber that closely resembles silk.

Q: What is the common name for polyethylene terephthalate?

A: The common name for polyethylene terephthalate is PET.

Q: Which synthetic fiber is used in making carpets and ropes?

A: Nylon is often used in making carpets and ropes due to its strong and durable nature.

Q: What is the process of converting monomers into polymers called?

A: The process of converting monomers into polymers is called polymerization.

Q: List two disadvantages of using synthetic fibers.

A: Synthetic fibers are not biodegradable and can cause environmental pollution during their production.

Q: What is the full form of PVC, a commonly used synthetic material?

A: PVC stands for Polyvinyl chloride.

Q: Why are synthetic fibers ironed at low temperatures?

A: Synthetic fibers have a low melting point, so ironing them at high temperatures can cause them to melt or burn.

Q: Describe the manufacturing process of synthetic fibers.

A: Synthetic fibers are manufactured by either melt spinning or wet spinning processes, where polymers are extruded through spinnerets.

Q: Name a synthetic fiber that does not wrinkle easily.

A: Polyester is a synthetic fiber that has excellent wrinkle resistance.

Q: What is the most widely used synthetic fiber in the textile industry?

A: Polyester is the most widely used synthetic fiber in the textile industry.

Q: Why are synthetic fibers less affected by moths and fungi?

A: Synthetic fibers are less affected by moths and fungi because they are not composed of organic materials.

Q: Can synthetic fibers be recycled?

A: Yes, synthetic fibers can be recycled, but the process is complex and requires specialized facilities.

Q: Which synthetic fiber is resistant to chemicals and stains?

A: Nylon is highly resistant to chemicals and stains.

Q: Why are synthetic fibers used in making sporting goods?

A: Synthetic fibers offer properties like durability, flexibility, and resistance to moisture, making them suitable for making sporting goods.

Q: What is the primary raw material used in the manufacturing of synthetic fibers?

A: The primary raw material used in the manufacturing of synthetic fibers is petroleum or coal.

Q: Why are synthetic fibers used in the medical field?

A: Synthetic fibers are used in the medical field due to their non-absorbent nature and their ability to be sterilized easily.

Q: How are synthetic fibers different from natural fibers in terms of elasticity?

A: Synthetic fibers tend to be more elastic than natural fibers.

Q: State one disadvantage of using rayon as a synthetic fiber.

A: Rayon tends to shrink and lose strength when wet.

Q: What is a thermoplastic material?

A: A thermoplastic material is a synthetic material that can be melted and reshaped numerous times without undergoing a chemical change.

Q: Why are synthetic fibers commonly used in upholstery fabrics?

A: Synthetic fibers have good colorfastness, resistance to wrinkling, and durability, which make them suitable for upholstery fabrics.

Q: Name the type of synthetic fiber that is fire-resistant.

A: Aramid fibers, such as Kevlar, are known for their fire-resistant properties.

Q: Why are synthetic fibers preferred over cotton in swimwear?

A: Synthetic fibers are preferred in swimwear as they do not absorb water easily, allowing the swimwear to dry quickly.

Q: How does the use of synthetic fibers affect the environment?

A: The production and disposal of synthetic fibers contribute to environmental pollution and take a long time to degrade.

Q: Which synthetic fiber is commonly used in making tracksuits and jackets?

A: Polyester is commonly used in making tracksuits and jackets.

Q: State one disadvantage of using nylon as a synthetic fiber.

A: Nylon has poor resistance to sunlight and can degrade when exposed to UV radiation.

Q: Which synthetic fiber is used in making parachutes and seat belts?

A: Nylon is used in making parachutes and seat belts due to its high strength and resistance.

Q: Why are synthetic fibers used in the automobile industry?

A: Synthetic fibers are used in the automobile industry for making upholstery, carpets, and other interior components due to their durability and ease of maintenance.

Q: How can synthetic fibers contribute to microplastic pollution?

A: Synthetic fibers shed microplastic particles when washed, which can enter water bodies and harm marine life.

Q: Name one synthetic fiber that is resistant to sunlight and weathering.

A: Acrylic is a synthetic fiber that is highly resistant to sunlight and weathering.

Q: What is the role of plasticizers in the production of synthetic fibers?

A: Plasticizers are added to make synthetic fibers softer and more flexible.

Q: Which synthetic fiber is used in making ropes for rock climbing?

A: Polypropylene is commonly used in making ropes for rock climbing due to its high strength and low stretch.

Q: How can we prevent the environmental impact of synthetic fibers?

A: Recycling of synthetic fibers, reducing their production, and opting for sustainable alternatives can help prevent their environmental impact.

Q: Name the synthetic fiber that is resistant to wrinkles and shrinkage.

A: Polyester is known for its wrinkle resistance and minimal shrinkage.

Q: Why are synthetic fibers preferred over natural fibers for making swimwear?

A: Synthetic fibers in swimwear can provide better stretch, resistance to chlorine and UV rays, and quicker drying.

Q: Can synthetic fibers be blended with natural fibers? If yes, why?

A: Yes, synthetic fibers can be blended with natural fibers to create fabrics with improved properties such as strength, durability, and wrinkle resistance.

Q: What are microfibers, and how are they related to synthetic fibers?

A: Microfibers are tiny fibers shed by synthetic fabrics during washing, and they are a type of microplastic pollution.

Q: Why are synthetic fibers used in making carpets for high foot-traffic areas?

A: Synthetic fibers offer durability, stain resistance, and easy maintenance, making them suitable for carpets in high foot-traffic areas.

Q: State one disadvantage of using acrylic as a synthetic fiber.

A: Acrylic is relatively less durable compared to some other synthetic fibers and may pill easily.

Q: How can we identify synthetic fibers?

A: Synthetic fibers can be identified by performing a burn test or through microscopic examination.

Q: Name a synthetic fiber commonly used in making athletic wear.

A: Spandex, also known as elastane, is a synthetic fiber commonly used in making athletic wear due to its excellent stretch and recovery properties.

Q: What is the purpose of adding dyes to synthetic fibers during manufacturing?

A: Adding dyes to synthetic fibers enhances their aesthetic appeal by providing a variety of colors.

Q: Why are synthetic fibers used in the production of non-stick cookware and electrical insulation?

A: Synthetic fibers, such as Teflon, are used in non-stick cookware and electrical insulation due to their high heat resistance and low friction properties.

Q: What is the role of additives in synthetic fiber production?

A: Additives are used to enhance specific properties of synthetic fibers, such as flame resistance, dyeability, or antistatic characteristics.

Chapter 4 Materials: Metals and Non-Metals

Question: Define metals and non-metals.

Solution: Metals are elements that have a shiny appearance and conduct heat and electricity. Non-metals are elements that are poor conductors of heat and electricity and do not have a shiny appearance.

Question: Name three physical properties of metals.

Solution: Three physical properties of metals are luster, malleability, and ductility.

Question: Give an example of each: (a) a metal that can be easily cut with a knife, (b) a metal that is liquid at room temperature.

Solution: (a) Sodium (b) Mercury

Question: What are metalloids?

Solution: Metalloids are elements that have properties of both metals and non-metals. They are often called semi-metals.

Question: Name two metalloids. Solution: Silicon and Germanium are two examples of metalloids.

Question: What is corrosion?

Solution: Corrosion is the process of gradual destruction of metals due to their reaction with substances in the environment.

Question: Name the gas produced when metals react with acids.

Solution: Hydrogen gas is produced when metals react with acids.

Question: What happens when metals react with oxygen?

Solution: Metals react with oxygen to form metal oxides.

Question: Identify one metal and one non-metal that exist in the liquid state at room temperature.

Solution: Mercury (metal) and Bromine (non-metal)

Question: What is the general trend in the reactivity of metals in the periodic table?

Solution: The reactivity of metals increases as we move down a group and decreases as we move across a period from left to right.

Question: Write one use of copper.

Solution: Copper is used for making electrical wires.

Question: Name the two non-metals that are used to make fertilizers.

Solution: Nitrogen and Phosphorus.

Question: Define the term 'alloy.'

Solution: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Question: What is the composition of the alloy 'bronze'?

Solution: Bronze is composed of copper and tin.

Question: How can the reaction of a metal and a non-metal be categorized?

Solution: The reaction between a metal and a non-metal is a redox reaction.

Question: What is the process of the chemical treatment of the surface of a metal called?

Solution: The process of the chemical treatment of the surface of a metal is called galvanization.

Question: Give an example of a metal that reacts with both dilute acids and alkalis.

Solution: Aluminium is an example of a metal that reacts with both dilute acids and alkalis.

Question: Define the term 'malleability.'

Solution: Malleability is the property of a metal by which it can be beaten into thin sheets.

Question: Which non-metal is necessary for combustion to occur?

Solution: Oxygen is necessary for combustion to occur.

Question: Define the term 'ductility.'

Solution: Ductility is the property of a metal by which it can be drawn into wires.

Question: Name two metals that can displace hydrogen from acids.

Solution: Zinc and Iron can displace hydrogen from acids.

Question: What happens when metals react with water?

Solution: Metals react with water to produce metal hydroxides and hydrogen gas.

Question: State one characteristic of non-metals.

Solution: Non-metals are generally brittle.

Question: What is the general trend in the physical properties of non-metals in the periodic table?

Solution: The physical properties of non-metals become more non-metallic as we move from left to right across a period.

Question: Give an example of an alloy.

Solution: Stainless steel is an example of an alloy.

Question: What is the chemical name of baking soda?

Solution: The chemical name of baking soda is sodium bicarbonate.

Question: Name the metal used for galvanization.

Solution: Zinc is used for galvanization.

Question: Define the term 'corrosion.'

Solution: Corrosion is the gradual destruction of metals by the action of air, moisture, or chemicals on their surface.

Question: What is the product obtained when a non-metal reacts with oxygen?

Solution: Non-metals react with oxygen to form non-metal oxides.

Question: Name one non-metal that exists in the gaseous state at room temperature.

Solution: Oxygen is a non-metal that exists in the gaseous state at room temperature.

Question: State two chemical properties of metals.

Solution: Metals react with acids to produce hydrogen gas and react with oxygen to form metal oxides.

Question: What is the product obtained when a metal reacts with acid?

Solution: When a metal reacts with an acid, the product obtained is a metal salt and hydrogen gas.

Question: Name the metal used for making electric wires.

Solution: Copper is used for making electric wires.

Question: Define the term 'brittleness.' Solution: Brittleness is the property of a substance by which it breaks or shatters easily when subjected to stress.

Question: What is the purpose of the coating of zinc on iron objects?

Solution: The coating of zinc on iron objects is done to prevent corrosion.

Question: State two uses of non-metals.

Solution: Two uses of non-metals are as fuels and in the manufacturing of fertilizers.

Question: What is the general trend in the reactivity of non-metals in the periodic table?

Solution: The reactivity of non-metals decreases as we move down a group and increases as we move from left to right across a period.

Question: Give an example of a metal that is used for galvanizing iron.

Solution: Zinc is used for galvanizing iron.

Question: Name the non-metal used for making matchsticks.

Solution: Phosphorus is used for making matchsticks.

Question: What is the product obtained when a non-metal reacts with water?

Solution: Non-metals generally do not react with water.

Question: Define the term 'reduction.'

Solution: Reduction is a chemical process in which there is a gain of electrons by an element, compound, or ion.

Question: Name a metal that is used for making electric fuse wires.

Solution: Lead is used for making electric fuse wires.

Question: How can you test whether a given substance is a metal or a non-metal?

Solution: Substances can be tested by their ability to conduct heat and electricity. If it conducts heat and electricity well, it is likely to be a metal.

Question: State the general properties of non-metals.

Solution: Non-metals are generally brittle, dull, and poor conductors of heat and electricity.

Question: Name the non-metal used for making fertilizers.

Solution: Nitrogen is used for making fertilizers.

Question: Define the term 'ductile.'

Solution: Ductile means the ability of a metal to be drawn or stretched into thin wires.

Question: What is the chemical name of quicklime?

Solution: The chemical name of quicklime is calcium oxide.

Question: Name two metals that are found in a pure state in nature.

Solution: Gold and Silver are two metals that are found in a pure state in nature.

Question: What is the general trend in the melting and boiling points of metals across the periodic table?

Solution: The melting and boiling points of metals generally increase as we move from left to right across a period.

Question: Name two physical properties of non-metals.

Solution: Two physical properties of non-metals are they are generally brittle and poor conductors of heat and electricity.

Chapter 5 Coal and Petroleum

What are fossil fuels?

Solution: Fossil fuels are natural resources formed from the remains of ancient plants and animals.

Name two examples of fossil fuels.

Solution: Coal and petroleum are two examples of fossil fuels.

Which gas is released during the burning of fossil fuels?

Solution: Carbon dioxide gas is released during the burning of fossil fuels.

What is the process of extracting petroleum from deep wells called?

Solution: The process of extracting petroleum from deep wells is called drilling.

Name the process used to convert dead plants into coal.

Solution: The process used to convert dead plants into coal is called carbonization.

Which type of coal has the highest carbon content?

Solution: Anthracite coal has the highest carbon content.

State one advantage of using coal as a fuel.

Solution: Coal is abundant and widely available.

State one disadvantage of burning fossil fuels.

Solution: Burning fossil fuels contributes to air pollution and the greenhouse effect.

What is the main source of petroleum?

Solution: The main source of petroleum is the remains of marine organisms.

Name the process by which petroleum is separated into different components.

Solution: The process by which petroleum is separated into different components is called fractional distillation.

Which fraction of crude oil is used for making tar?

Solution: The residue left after fractional distillation, the heaviest fraction, is used for making tar.

What is natural gas primarily composed of?

Solution: Natural gas is primarily composed of methane.

What is the chemical formula of methane?

Solution: The chemical formula of methane is CH4.

Define the term 'refinery.'

Solution: A refinery is a facility where crude oil is converted into useful products like gasoline, diesel, and kerosene.

Give an example of a non-renewable resource.

Solution: Coal is an example of a non-renewable resource.

What are the by-products obtained during the processing of petroleum?

Solution: By-products obtained during the processing of petroleum are LPG, petrol, diesel, and wax.

Name the process of heating coal in the absence of air.

Solution: The process of heating coal in the absence of air is called destructive distillation.

What is the importance of coal gas?

Solution: Coal gas is important as it is used for lighting and heating purposes.

Name two environmental problems associated with coal mining.

Solution: Air and water pollution are two environmental problems associated with coal mining.

What is the cleanest form of coal?

Solution: Anthracite coal is considered the cleanest form of coal.

Explain the term 'petrochemicals.'

Solution: Petrochemicals are chemical compounds derived from petroleum for industrial use.

Why is coal known as a fossil fuel?

Solution: Coal is known as a fossil fuel because it is formed from the remains of prehistoric plants.

State one difference between coal and petroleum.

Solution: Coal is a solid fossil fuel, whereas petroleum is a liquid fossil fuel.

What is the main constituent of natural gas?

Solution: The main constituent of natural gas is methane.

Why is it necessary to conserve fossil fuels?

Solution: Fossil fuels are finite resources, and their overuse can lead to their depletion. Conservation is necessary for sustainable energy resources.

Name two alternative sources of energy to replace fossil fuels.

Solution: Solar energy and wind energy are two alternative sources of energy to replace fossil fuels.

How does the carbonization of plant material occur?

Solution: Plant material undergoes high temperature and pressure over millions of years to undergo carbonization.

State one advantage of using natural gas as a fuel.

Solution: Natural gas is a cleaner fuel, producing less pollution compared to coal and petroleum.

How can coal mines affect the environment?

Solution: Coal mines can lead to deforestation, air pollution, and water pollution.

Name the process by which coal is converted into coke.

Solution: The process by which coal is converted into coke is called 'heating in the absence of air.'

What are the characteristics of peat?

Solution: Peat is a low-carbon, high-moisture, and fibrous form of partially decayed vegetation.

How can petroleum spills affect marine life?

Solution: Petroleum spills can harm marine life by contaminating water with toxic substances.

What are the advantages of using natural gas as a fuel for vehicles?

Solution: Natural gas is a cheaper and cleaner fuel for vehicles, emitting lesser pollutants compared to petrol or diesel.

Explain the term 'cracking' in relation to petroleum refining.

Solution: Cracking refers to the process of breaking down heavier hydrocarbon molecules into lighter ones during petroleum refining.

Which fraction of petroleum is used as fuel for rocket engines?

Solution: Kerosene is the fraction of petroleum used as fuel for rocket engines.

How can coal mining impact the health of miners?

Solution: Coal miners may develop respiratory issues due to inhaling coal dust and gases present in mines.

Define the term 'tar.'

Solution: Tar is a black, sticky, and highly viscous material obtained as a residue during petroleum refining.

Which type of coal contains the least amount of carbon?

Solution: Lignite coal contains the least amount of carbon.

What is the chemical formula of petroleum?

Solution: Petroleum is a complex mixture of hydrocarbons and does not have a specific chemical formula.

How is coal formed? Explain briefly.

Solution: Coal is formed from the remains of prehistoric plants that accumulated in swamps, underwent pressure, and transformed into the fossil fuel over millions of years.

Name the raw material used to make coal gas.

Solution: Coal is the raw material used to make coal gas.

Mention one harmful component present in coal gas.

Solution: Carbon monoxide is a harmful component present in coal gas.

What are the environmental impacts of burning fossil fuels?

Solution: Burning fossil fuels can contribute to air pollution, global warming, and climate change.

How does petroleum exploration take place?

Solution: Petroleum exploration involves geological surveys, seismic surveys, drilling test wells, and analyzing rock samples.

Explain the term 'reserves' when it comes to fossil fuels.

Solution: Reserves refer to the known deposits of fossil fuels that can be economically extracted using existing technologies.

Name the two types of coal.

Solution: The two types of coal are hard coal (anthracite and bituminous coal) and brown coal (lignite).

What is the octane number used for in petrol?

Solution: The octane number in petrol indicates its resistance to knocking or pinging in an internal combustion engine.

Name one pollutant released during the burning of coal.

Solution: Sulphur dioxide (SO2) is a pollutant released during the burning of coal.

How can the quality of coal be determined?

Solution: The quality of coal can be determined by its carbon content, calorific value, moisture content, and ash content.

How can we reduce our dependence on fossil fuels?

Solution: We can reduce our dependence on fossil fuels by adopting renewable energy sources, conserving energy, and promoting energy-efficient technologies.

Chapter 6 Combustion and Flame

What is combustion?

Solution: Combustion is a chemical process that occurs when a substance reacts with oxygen, releasing heat and light.

What is a fuel?

Solution: A fuel is a substance that undergoes combustion to produce heat or energy.

Give three examples of solid fuels.

Solution: Wood, coal, and charcoal are examples of solid fuels.

Why do we need to control the amount of air supplied during combustion?

Solution: Controlling the amount of air supplied during combustion ensures efficient burning and prevents the wastage of fuel.

Define ignition temperature.

Solution: Ignition temperature is the minimum temperature required to ignite or start a combustion process.

Name two gases that are produced during combustion.

Solution: Carbon dioxide and carbon monoxide are two gases produced during combustion.

What is a flame?

Solution: A flame is a visible gaseous part of a burning substance, accompanied by heat and light energy.

How many zones are present in a flame? Name them.

Solution: Four zones are present in a flame: the dark zone, the non-luminous zone, the luminous zone, and the outermost zone.

Why is LPG considered a better fuel than wood?

Solution: LPG (liquefied petroleum gas) is considered a better fuel than wood because it produces more heat per unit mass, burns cleanly, and is easy to handle.

What safety precautions should be followed while using LPG?

Solution: Some safety precautions while using LPG include keeping the cylinder in an upright position, checking for gas leaks with soapy water, and not using a flame to check for leaks.

Name the unit in which calorific value is measured.

Solution: The unit in which calorific value is measured is kilojoules per kilogram (kJ/kg).

Give an example of a self-sustained combustion reaction.

Solution: The burning of a candle is an example of self-sustained combustion.

What is the role of a fire extinguisher?

Solution: The role of a fire extinguisher is to control or extinguish fires by removing one or more elements necessary for combustion.

Why are some substances considered non-combustible?

Solution: Non-combustible substances are those that do not undergo combustion or burn.

What is a fire triangle?

Solution: A fire triangle represents the three components necessary for a fire to occur: fuel, oxygen, and heat.

State the principle behind the working of a fire extinguisher.

Solution: The principle behind the working of a fire extinguisher is to remove oxygen or cool down the fuel, interrupting the combustion process.

How does candle wick help in burning?

Solution: The candle wick draws the molten wax to its tip through capillary action, providing a steady supply of fuel to burn.

What is the full form of LPG?

Solution: The full form of LPG is liquefied petroleum gas.

Explain the process of rusting.

Solution: Rusting is the process of corrosion that occurs when iron or steel comes in contact with oxygen and moisture, resulting in the formation of iron oxide (rust).

Why do we use a fire blanket for extinguishing small fires?

Solution: Fire blankets are used to smother small fires by cutting off the supply of oxygen, thereby extinguishing the fire.

What is spontaneous combustion?

Solution: Spontaneous combustion is the ignition of a substance without the application of an external heat source, typically due to heat generated by a chemical reaction.

Define flammable substances.

Solution: Flammable substances are those that can readily catch fire and burn easily.

How does the increase in pressure affect the ignition temperature of a substance?

Solution: An increase in pressure generally lowers the ignition temperature of a substance.

What is the purpose of a spark arrestor in a chimney?

Solution: The purpose of a spark arrestor in a chimney is to prevent sparks or embers from coming out and starting a fire.

How does a matchstick ignite?

Solution: A matchstick ignites when the chemicals on the match head, such as sulfur and red phosphorus, react with friction on the striking surface, producing enough heat to ignite the matchstick.

Give three examples of liquid fuels.

Solution: Petrol, diesel, and kerosene are examples of liquid fuels.

What is the role of a fire alarm system?

Solution: The role of a fire alarm system is to detect the presence of smoke or fire and alert people to evacuate and take necessary actions.

How is an LPG leak detected?

Solution: LPG leaks can be detected by applying a soapy water solution to the suspected area. If bubbles form, it indicates a leak.

Define the terms 'endothermic' and 'exothermic' reactions.

Solution: Endothermic reactions absorb heat from their surroundings, while exothermic reactions release heat into their surroundings.

Why do we use a fire screen in front of a fireplace?

Solution: A fire screen in front of a fireplace is used to prevent sparks and embers from coming out and causing accidental fires.

Why does the wick burn completely while the rest of the candle does not?

Solution: The wick of a candle burns completely because it is the part constantly in contact with the flame, while the rest of the candle does not burn fully due to lack of oxygen.

How can you control a small kitchen fire caused by oil/grease?

Solution: A small kitchen fire caused by oil/grease can be controlled by covering the pan with a lid or using a fire extinguisher specifically designed for oil/grease fires.

Why is water not used to extinguish oil or electrical fires?

Solution: Water is not used to extinguish oil or electrical fires because it can spread the oil fire or conduct electricity, respectively, making the situation worse.

Name the three common types of fire extinguishers.

Solution: The three common types of fire extinguishers are water, foam, and CO2 (carbon dioxide).

How can you prevent the risk of fires in the kitchen?

Solution: Some preventive measures to reduce the risk of kitchen fires include never leaving cooking unattended, keeping flammable substances away from heat sources, and using kitchen appliances correctly.

What are the disadvantages of using fossil fuels as a source of energy?

Solution: Some disadvantages of using fossil fuels as a source of energy include air pollution, greenhouse gas emissions, and their limited availability.

What is the importance of proper ventilation in combustion processes?

Solution: Proper ventilation ensures the supply of oxygen needed for combustion, prevents the buildup of harmful gases, and promotes complete burning of the fuel.

How does the use of fossil fuels contribute to climate change?

Solution: The burning of fossil fuels releases carbon dioxide into the atmosphere, which contributes to the greenhouse effect and climate change.

What are the environmental impacts of incomplete combustion?

Solution: Incomplete combustion can lead to the formation of harmful gases like carbon monoxide and particulate matter, which contribute to air pollution and respiratory problems.

Explain the term 'smokeless fuel.'

Solution: Smokeless fuels are those that produce very little or no smoke when burned, reducing air pollution and environmental impact.

How can you differentiate between a flame and a glowing flame?

Solution: A flame emits light and heat, while a glowing flame only emits light without heat.

What precautions should be taken while using a kerosene lamp?

Solution: Some precautions while using a kerosene lamp include keeping it away from flammable substances, checking for leaks, and maintaining proper ventilation.

Why are fire drills conducted in schools or workplaces?

Solution: Fire drills are conducted to ensure preparedness and practice evacuation procedures in case of a fire emergency.

Explain the term 'controlled combustion.'

Solution: Controlled combustion refers to the deliberate regulation and management of the process of burning, allowing for maximum energy extraction and minimal waste.

Why should flammable substances be stored in well-ventilated areas?

Solution: Flammable substances should be stored in well-ventilated areas to prevent the accumulation of flammable vapors, reducing the risk of fire or explosion.

How does the use of biomass as a fuel contribute to deforestation?

Solution: The use of biomass as a fuel can contribute to deforestation if excessive harvesting of wood or plants for fuel results in the depletion of forests.

What is the purpose of a chimney in a fireplace?

Solution: The chimney in a fireplace provides an outlet for the smoke and gases produced during combustion, ensuring proper ventilation and preventing the buildup of harmful substances.

Explain the difference between natural and artificial combustion.

Solution: Natural combustion occurs spontaneously, while artificial combustion requires the application of external heat or ignition sources.

How can you stop a fire caused by an electrical short circuit?

Solution: In case of a fire caused by an electrical short circuit, the power supply should be immediately turned off, and a fire extinguisher suitable for electrical fires should be used.

What safety measures can be taken to avoid accidental fires at home?

Solution: Some safety measures to avoid accidental fires at home include keeping flammable substances away from heat sources, ensuring proper ventilation, and installing smoke alarms and fire extinguishers in active areas.

Chapter 7 Conservation of Plants and Animals

What is biodiversity?

Solution: Biodiversity refers to the variety of different species of plants, animals, and microorganisms present in an ecosystem.

Define extinction.

Solution: Extinction is the complete disappearance of a species from the Earth.

What is the role of forests in maintaining the balance of nature?

Solution: Forests are crucial for maintaining the balance of nature as they provide habitats for numerous plant and animal species, regulate climate, purify air and water, and prevent soil erosion.

Explain the concept of deforestation.

Solution: Deforestation refers to the clearing, removal, or destruction of forests, usually for the purpose of agriculture, industrialization, or urbanization.

What are the consequences of deforestation?

Solution: Deforestation leads to soil erosion, loss of biodiversity, climate change, increased greenhouse gas emissions, and disruption of ecological balance.

How can we conserve forests?

Solution: Forest conservation can be achieved by promoting afforestation and reforestation programs, implementing sustainable logging practices, and creating awareness about the importance of forests.

What are the main causes of wildlife extinction?

Solution: The main causes of wildlife extinction include habitat destruction, poaching, pollution, climate change, and introduction of invasive species.

What is the importance of wildlife conservation?

Solution: Wildlife conservation helps in maintaining the ecological balance, preserving biodiversity, and ensuring the survival of various plant and animal species.

How can we contribute to wildlife conservation?

Solution: We can contribute to wildlife conservation by supporting initiatives like wildlife sanctuaries, national parks, adopting eco-friendly practices, promoting awareness, and preventing illegal trade.

Explain the concept of the Red List of IUCN.

Solution: The Red List of IUCN (International Union for Conservation of Nature) is a list that categorizes species based on their conservation status, ranging from least concern to extinct.

Name three critically endangered animal species.

Solution: Examples of critically endangered species are the Sumatran tiger, Black rhinoceros, and Hawksbill turtle.

What is the importance of plant conservation?

Solution: Plant conservation is important to maintain the biodiversity, provide food, medicine, and other resources, and prevent soil erosion.

Define endemism.

Solution: Endemism refers to the occurrence of a species exclusively in a particular geographical area and nowhere else.

What are the causes of soil erosion?

Solution: Soil erosion can be caused by deforestation, improper agricultural practices, overgrazing, construction, and water or wind action.

What are the measures to control soil erosion?

Solution: Measures to control soil erosion include afforestation, contour plowing, terracing, crop rotation, and the use of windbreaks.

Explain the concept of wildlife sanctuary.

Solution: A wildlife sanctuary is an area specifically designated for the protection and conservation of wildlife species and their habitats.

Differentiate between a sanctuary and a national park.

Solution: While both sanctuaries and national parks are dedicated to the conservation of flora and fauna, the major difference lies in the level of human intervention allowed. Sanctuaries allow for more human activities, whereas national parks have stricter regulations.

What is an exotic species?

Solution: An exotic species refers to a plant or animal species that is introduced into an ecosystem where it is not native.

How can we conserve endangered species?

Solution: Endangered species can be conserved through habitat protection, captive breeding programs, public awareness campaigns, and legislation to control illegal activities.

Explain the concept of sustainable development. Solution: Sustainable development refers to the use of resources in a way that meets the needs of the present generation without compromising the needs of future generations.

What is the importance of wetland conservation?

Solution: Wetland conservation is important as wetlands act as natural water filters, provide habitat for various species, help in flood control, and regulate climate.

Define poaching.

Solution: Poaching is the illegal hunting, capturing, or killing of wildlife for commercial or recreational purposes.

What are the consequences of poaching? Solution: Poaching leads to the decline of wildlife populations, disturbance of ecological balance, loss of biodiversity, and disruption of food chains.

What is the role of national parks in wildlife conservation? Solution: National parks play a crucial role in protecting and conserving the natural habitats of various plants and animal species.

How can we reduce air pollution? Solution: Air pollution can be reduced by promoting the use of clean energy sources, reducing industrial emissions, improving vehicle emission standards, and creating awareness about the importance of clean air.

What are the measures to conserve marine ecosystems?

Solution: Measures to conserve marine ecosystems include promoting sustainable fishing practices, establishing marine protected areas, reducing pollution, and regulating coastal development.

How can genetic diversity be conserved?

Solution: Genetic diversity can be conserved through the establishment of seed banks, preservation of germplasm, and breeding programs.

Define the term 'ecosystem'.

Solution: An ecosystem is a community of living organisms (plants, animals, and microorganisms) interacting with each other and with the physical environment in a particular area.

What is the concept of sustainable agriculture?

Solution: Sustainable agriculture refers to the practice of farming that aims to meet the current and future agricultural needs while preserving the environment and protecting natural resources.

What is the importance of pollinators in plant conservation?

Solution: Pollinators, such as bees and butterflies, play a vital role in plant reproduction by transferring pollen from the male parts to the female parts of flowers, thus facilitating the production of seeds and fruits.

Explain the concept of seed banks.

Solution: Seed banks are institutions that store seeds of various plant species to conserve their genetic diversity and protect them from potential extinction.

What is the significance of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)?

Solution: CITES is an international agreement aimed at regulating and monitoring the trade of endangered plant and animal species to ensure their survival.

What are the measures to conserve water resources?

Solution: Measures to conserve water resources include promoting water-efficient practices, reducing water wastage, rainwater harvesting, and wastewater treatment.

Explain the concept of the food chain and food web.

Solution: A food chain represents the transfer of energy from one organism to another, starting with the producer (plants) and ending with the top consumer. A food web is a more complex representation of interconnected food chains in an ecosystem.

Define the term 'habitat'.

Solution: A habitat is the natural environment where a particular plant, animal, or organism lives and obtains the resources and conditions necessary for its survival.

What are the advantages of afforestation?

Solution: Afforestation helps in soil conservation, providing habitat for wildlife, reducing the concentration of greenhouse gases, and mitigating the effects of climate change.

What is the role of zoos in conservation efforts?

Solution: Zoos contribute to conservation efforts by captive breeding of endangered species, promoting education and awareness, and conducting research for species reintroduction programs.

Explain the concept of the ozone layer and its importance.

Solution: The ozone layer is a protective layer of ozone gas in the Earth's stratosphere that absorbs most of the sun's harmful ultraviolet (UV) radiation. It is important as it prevents excessive UV radiation from reaching the Earth's surface, which can cause various health and environmental problems.

What are the measures to control air pollution?

Solution: Measures to control air pollution include promoting the use of clean energy sources, implementing emission control technologies, reducing industrial emissions, and improving vehicle emission standards.

What is the role of NGOs in conservation efforts?

Solution: NGOs (Non-Governmental Organizations) play a significant role in conservation efforts through advocacy, awareness campaigns, community participation, and providing financial and technical support.

Differentiate between a herbivore and a carnivore.

Solution: Herbivores are animals that primarily feed on plants, while carnivores are animals that primarily feed on other animals.

What is the importance of biosphere reserves?

Solution: Biosphere reserves are designated areas designed to promote conservation, sustainable development, and scientific research. They help in preserving biodiversity, maintaining ecological balance, and supporting local communities.

Explain the concept of the Green Revolution in agriculture.

Solution: The Green Revolution refers to the period of technological advancements in agriculture, leading to increased crop productivity through the use of highyielding varieties, irrigation, and agrochemicals.

What are the measures to protect endangered plant species?

Solution: Measures to protect endangered plant species include preserving their habitats, implementing strict regulations on collection and trade, establishing protected areas, and promoting ex situ conservation.

Define the term 'renewable resources'.

Solution: Renewable resources are natural resources such as solar energy, wind energy, and hydroelectric energy that can be replenished or regenerated naturally over time.

What is the importance of coral reef conservation?

Solution: Coral reef conservation is important as coral reefs support numerous marine species, provide protection against coastal erosion, and have significant economic value through tourism and fisheries.

What are the consequences of water pollution?

Solution: Water pollution leads to the contamination of water bodies, harming aquatic life, disrupting ecosystems, and posing risks to human health.

Explain the concept of captive breeding programs.

Solution: Captive breeding programs involve the breeding of endangered species in controlled environments such as zoos or breeding centers to increase their population size and genetic diversity.

What is the significance of the Ramsar Convention?

Solution: The Ramsar Convention is an international treaty aimed at conserving and protecting wetlands of international importance, primarily as habitats for waterbirds.

What is the role of the government in conservation efforts? Solution: The government plays a crucial role in conservation efforts by enacting and enforcing laws, creating protected areas, conducting research, and promoting sustainable development practices.

Chapter 8 Cell - Structure and Functions

Q: What is a cell? A: A cell is the basic structural and functional unit of all living organisms.

Q: What are the three main parts of a cell?

A: The three main parts of a cell are the cell membrane, cytoplasm, and nucleus.

Q: What is the function of the cell membrane?

A: The cell membrane controls the movement of substances in and out of the cell.

Q: What is the function of the cytoplasm?

A: The cytoplasm is a jelly-like substance that holds the cell organelles and helps in cellular processes.

Q: What is the function of the nucleus?

A: The nucleus is the control center of the cell that contains DNA and regulates cell activities.

Q: Name two types of cells based on the presence of a nucleus.

A: Cells are classified as prokaryotic (without a nucleus) and eukaryotic (with a nucleus).

Q: What are cell organelles?

A: Cell organelles are specialized structures within a cell that perform specific functions.

Q: Name two organelles involved in the synthesis of proteins.

A: Ribosomes and endoplasmic reticulum are involved in protein synthesis.

Q: What is the function of the mitochondria? A: The mitochondria are responsible for producing energy for the cell through cellular respiration.

Q: What is the function of the Golgi apparatus?

A: The Golgi apparatus modifies, sorts, and packages proteins for transport within or outside the cell.

Q: What is the function of the vacuole?

A: The vacuole stores water, nutrients, and waste materials in the cell.

Q: Name the cell organelle found only in plant cells.

A: Chloroplasts are found only in plant cells and are responsible for photosynthesis.

Q: What is photosynthesis?

A: Photosynthesis is the process by which plants convert sunlight, water, and carbon dioxide into glucose and oxygen.

Q: What is the main function of the cell wall?

A: The cell wall provides structure, support, and protection to plant cells.

Q: What are the functions of the endoplasmic reticulum?

A: The endoplasmic reticulum helps in the synthesis and transportation of proteins and lipids.

Q: What is the function of lysosomes?

A: Lysosomes contain enzymes that break down waste materials and cellular debris.

Q: Define diffusion.

A: Diffusion is the movement of molecules from an area of high concentration to an area of low concentration.

Q: What is osmosis?

A: Osmosis is the movement of water molecules across a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration.

Q: Explain the difference between plant and animal cells.

A: Plant cells have cell walls, chloroplasts, and a large central vacuole, while animal cells do not.

Q: What is the difference between prokaryotic and eukaryotic cells?

A: Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and membrane-bound organelles.

Q: What is cell division?

A: Cell division is the process by which cells reproduce and create new cells.

Q: Name the two types of cell division.

A: The two types of cell division are mitosis and meiosis.

Q: What is mitosis?

A: Mitosis is the process of cell division in which a single cell divides to produce two identical daughter cells.

Q: Explain the phases of mitosis.

A: The phases of mitosis are prophase, metaphase, anaphase, and telophase.

Q: What is meiosis?

A: Meiosis is the process of cell division that produces gametes (sex cells) with half the chromosome number of the parent cell.

Q: What is the importance of meiosis?

A: Meiosis allows for genetic variation and is responsible for sexual reproduction.

Q: Define cell respiration.

A: Cell respiration is the process by which cells break down glucose to release energy in the form of ATP.

Q: What is the difference between aerobic and anaerobic respiration?

A: Aerobic respiration requires oxygen, while anaerobic respiration occurs in the absence of oxygen.

Q: Explain the concept of cellular transport.

A: Cellular transport refers to the movement of substances across cell membranes.

Q: Name three types of cellular transport.

A: The three types of cellular transport are passive transport, active transport, and facilitated diffusion.

Q: Define active transport.

A: Active transport is the movement of molecules across a cell membrane that requires energy.

Q: What is passive transport?

A: Passive transport is the movement of molecules across a cell membrane without the expenditure of energy.

Q: Explain the process of endocytosis.

A: Endocytosis is the process by which cells engulf substances by forming vesicles.

Q: What is exocytosis?

A: Exocytosis is the process by which cells release substances outside the cell through vesicles.

Q: Define tissue.

A: Tissue is a group of cells with similar structure and function.

Q: Name the four types of animal tissues.

A: The four types of animal tissues are epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

Q: What is the function of epithelial tissue?

A: Epithelial tissue covers and protects body surfaces and forms glands.

Q: Define organ.

A: An organ is a group of tissues working together to perform a specific function.

Q: Name the five vital organs in the human body.

A: The five vital organs in the human body are the heart, lungs, liver, kidneys, and brain.

Q: What is the function of the circulatory system?

A: The circulatory system transports oxygen, nutrients, hormones, and waste materials throughout the body.

Q: Name the four components of the circulatory system.

A: The four components of the circulatory system are the heart, blood vessels, blood, and lymph.

Q: What is the function of red blood cells?

A: Red blood cells carry oxygen to body tissues and remove carbon dioxide.

Q: Define unicellular and multicellular organisms.

A: Unicellular organisms are made up of a single cell, while multicellular organisms are composed of multiple cells.

Q: State three differences between plant and animal cells.

A: Plant cells have a cell wall, chloroplasts, and a large central vacuole, while animal cells do not have these structures.

Q: What is the role of ribosomes in cells?

A: Ribosomes are involved in protein synthesis.

Q: What is the function of the nucleolus? A: The nucleolus is responsible for producing ribosomes.

Q: Explain the importance of cells in living organisms.

A: Cells are the building blocks of living organisms and perform various functions necessary for life.

Q: What are stem cells?

A: Stem cells are unspecialized cells that have the ability to develop into different types of cells in the body.

Q: Define autotrophs and heterotrophs.

A: Autotrophs are organisms that can produce their own food, while heterotrophs depend on other organisms for food.

Q: Why is the cell called the structural and functional unit of life?

A: The cell is called the structural and functional unit of life because it is the smallest unit capable of performing all essential functions of an organism.

Chapter 9 Reproduction in Animals

Q: What is reproduction?

A: Reproduction is the process by which living organisms produce new individuals of the same kind.

Q: What are the two types of reproduction?

A: The two types of reproduction are sexual reproduction and asexual reproduction.

Q: Define sexual reproduction.

A: Sexual reproduction is a type of reproduction that involves the fusion of male and female gametes to produce offspring.

Q: Define asexual reproduction.

A: Asexual reproduction is a type of reproduction that does not involve the fusion of gametes and results in offspring identical to the parent.

Q: Mention a few examples of animals that reproduce through sexual reproduction.

A: Examples include humans, dogs, cats, and birds.

Q: Mention a few examples of animals that reproduce through asexual reproduction.

A: Examples include bacteria, yeast, hydra, and planarians.

Q: What are gametes?

A: Gametes are reproductive cells that are involved in sexual reproduction. Sperm is the male gamete, and egg or ovum is the female gamete.

Q: Where are sperm cells produced in males?

A: Sperm cells are produced in the testes.

Q: Where are egg cells produced in females?

A: Egg cells are produced in the ovaries.

Q: What is fertilization?

A: Fertilization is the process of fusion of male and female gametes to form a zygote.

Q: What is a zygote?

A: A zygote is a fertilized egg formed by the fusion of male and female gametes.

Q: Explain the process of external fertilization.

A: External fertilization occurs outside the body of the organisms. The male and female release their gametes into the environment, where fertilization takes place.

Q: Give an example of an animal that reproduces through external fertilization.

A: Fishes are an example of animals that reproduce through external fertilization.

Q: Explain the process of internal fertilization.

A: Internal fertilization occurs inside the body of the organisms. The male transfers sperm into the female reproductive system, where fertilization takes place.

Q: Give an example of an animal that reproduces through internal fertilization.

A: Mammals, including humans, reproduce through internal fertilization.

Q: What is asexual reproduction by budding?

A: Budding is a form of asexual reproduction in which a new individual grows as an outgrowth from the parent organism.

Q: Give an example of an animal that reproduces through budding.

A: Hydra is an example of an animal that reproduces through budding.

Q: What is regeneration in animals?

A: Regeneration is the ability of certain organisms to replace or regrow lost body parts.

Q: Give an example of an animal that can regenerate body parts.

A: Starfish is an example of an animal that can regenerate its lost body parts.

Q: What are oviparous animals?

A: Oviparous animals are the ones that lay eggs.

Q: Give an example of an oviparous animal.

A: Birds are examples of oviparous animals.

Q: What are viviparous animals?

A: Viviparous animals are the ones that give birth to live young ones.

Q: Give an example of a viviparous animal.

A: Humans and most mammals are examples of viviparous animals.

Q: What is metamorphosis?

A: Metamorphosis is a process of transformation that some animals undergo during their life cycle.

Q: Give an example of an animal that undergoes complete metamorphosis.

A: Butterflies are an example of animals that undergo complete metamorphosis.

Q: Define adolescence.

A: Adolescence is the stage of life between childhood and adulthood.

Q: What is puberty?

A: Puberty is the stage during adolescence when the body undergoes physical changes and sexual maturity is achieved.

Q: What are secondary sexual characteristics?

A: Secondary sexual characteristics are the physical features that develop during puberty and differentiate between males and females.

Q: Give examples of secondary sexual characteristics in males.

A: Examples include deepening of voice, facial hair growth, and Adam's apple enlargement.

Q: Give examples of secondary sexual characteristics in females.

A: Examples include breast development, widening of hips, and the onset of menstruation.

Q: What is menstruation?

A: Menstruation is the monthly shedding of the lining of the uterus in females.

Q: What is the reproductive system?

A: The reproductive system is a set of organs and structures involved in the production of offspring.

Q: What are the male reproductive organs?

A: The male reproductive organs include testes, vas deferens, seminal vesicles, prostate gland, and penis.

Q: What are the female reproductive organs?

A: The female reproductive organs include ovaries, Fallopian tubes, uterus, cervix, and vagina.

Q: What is the menstrual cycle?

A: The menstrual cycle is a monthly hormonal cycle in females that prepares the body for pregnancy.

Q: What is the purpose of the menstrual cycle?

A: The purpose of the menstrual cycle is to prepare the uterus for the implantation of a fertilized egg.

Q: What is a menstrual period?

A: A menstrual period is the bleeding phase of the menstrual cycle, during which the uterus sheds its lining.

Q: What is a menstrual flow?

A: Menstrual flow refers to the blood and tissue that is discharged from the uterus during a menstrual period.

Q: What is contraception?

A: Contraception refers to the methods used to prevent pregnancy.

Q: Name a few contraceptive methods.

A: Condoms, birth control pills, intrauterine devices (IUDs), and diaphragms are some examples of contraceptive methods.

Q: What is sexually transmitted infection (STI)?

A: Sexually transmitted infections are infections that are transmitted through sexual contact.

Q: Give examples of sexually transmitted infections.

A: Examples include HIV/AIDS, gonorrhea, syphilis, and chlamydia.

Q: What is fertilization in humans?

A: Fertilization in humans is the process of the union of sperm and egg in the Fallopian tube.

Q: Where does the fertilized egg implant in humans?

A: The fertilized egg implants in the lining of the uterus.

Q: What is a pregnancy?

A: Pregnancy is the period during which a fertilized egg develops into an offspring inside a female's body.

Q: What is a zygote?

A: A zygote is a fertilized egg formed by the fusion of sperm and egg.

Q: What is an embryo?

A: An embryo is the stage of development of a multicellular organism from fertilization until it becomes a fetus.

Q: What is a fetus?

A: A fetus is the stage of prenatal development from the 9th week post-fertilization until birth.

Q: How long is the gestation period in humans?

A: The gestation period in humans is typically around 9 months or 40 weeks.

Q: What happens during labor and delivery?

A: During labor and delivery, the muscles of the uterus contract to push the fetus out of the mother's body.

Chapter 10 Reaching the Age of Adolescence

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Chapter 11 Force and Pressure

What is force?

Solution: Force is a push or pull that can change the state of motion or shape of an object.

State the SI unit of force.

Solution: The SI unit of force is Newton (N).

Define pressure. Solution: Pressure is the amount of force applied per unit area.

What is the formula for pressure?

Solution: Pressure = Force/Area.

Which instrument is used to measure force?

Solution: A spring balance is used to measure force.

How is force measured?

Solution: Force is measured using a spring balance in Newton (N).

Why does a book resting on a table not move?

Solution: The book does not move because the force of gravity pulling it down is balanced by the upward force of the table.

Give an example of a contact force.

Solution: Pushing a wall, kicking a football, etc., are examples of contact forces.

What is gravitational force?

Solution: Gravitational force is the force of attraction between two objects due to their mass.

Mention an example of a non-contact force.

Solution: Magnetism is an example of a non-contact force.

State the principle of moments.

Solution: The principle of moments states that for equilibrium, the sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point.

What is friction?

Solution: Friction is the force that opposes the motion between two surfaces in contact.

How does friction help us while walking?

Solution: Friction helps us to walk by providing a grip between our shoes and the ground, preventing us from slipping.

What factors affect friction?

Solution: The factors affecting friction are the nature of surfaces, the roughness of surfaces, and the force pressing the surfaces together.

Define air resistance.

Solution: Air resistance is the force exerted by air on a moving object, acting in the opposite direction to its motion.

Why does a parachute help in safe landing?

Solution: A parachute increases air resistance, slowing down the speed of the falling object and ensuring a safer landing.

Explain buoyancy.

Solution: Buoyancy is the upward force exerted on an object immersed in a fluid (liquid or gas).

What is Archimedes' principle?

Solution: Archimedes' principle states that an object submerged in a fluid experiences an upward force equal to the weight of the fluid it displaces.

Why do objects float or sink in water?

Solution: Objects float or sink in water based on whether their density is less than or greater than that of water.

State Pascal's law.

Solution: Pascal's law states that a change in pressure at any point in an enclosed fluid is transmitted equally to all parts of the fluid.

Why are hydraulic systems used in braking systems?

Solution: Hydraulic systems are used in braking systems because the force applied by the driver on the brake pedal is multiplied to apply a greater force to the brakes.

How is pressure related to the area of contact?

Solution: Pressure is inversely related to the area of contact; as the area decreases, the pressure increases and vice versa.

What is the largest unit of pressure?

Solution: The largest unit of pressure is atmosphere (atm).

Why is it easier to cut wood with a sharp knife rather than a blunt one?

Solution: It is easier to cut wood with a sharp knife because a sharp knife has a smaller contact area, thus exerting more pressure on the wood.

Explain the concept of fluid pressure.

Solution: Fluid pressure is the pressure exerted by a liquid or gas, which depends on the height of the fluid column and the density of the fluid.

Why does the pressure decrease as we go higher up in the atmosphere?

Solution: The pressure decreases with altitude because the weight of the air above decreases, resulting in lower pressure.

What is the unit of pressure in the metric system?

Solution: The unit of pressure in the metric system is Pascal (Pa).

Give an example of an object that experiences zero buoyant force in water.

Solution: An object with the same density as water experiences zero buoyant force and neither floats nor sinks.

What is the relationship between weight and mass?

Solution: Weight is the force exerted on an object due to gravity, while mass is the amount of matter in an object. Weight depends on mass and acceleration due to gravity.

Why does a sharp needle easily penetrate the surface of water?

Solution: A sharp needle easily penetrates the surface of water because it reduces the contact area, thus reducing the upward force of surface tension.

What is the importance of thumb in our hand?

Solution: The thumb is opposable, which means it can move against the other fingers. This allows us to grasp and hold objects with precision.

Why do we feel lighter in an elevator when it starts going up?

Solution: We feel lighter in an elevator when it starts going up because the upward acceleration reduces the normal force on our body, resulting in a feeling of reduced weight.

Explain the action and reaction forces involved when a person jumps from a height.

Solution: When a person jumps from a height, the action force is the person pushing against the ground, and the reaction force is the ground pushing the person upward.

Why do heavy vehicles have wider tires?

Solution: Heavy vehicles have wider tires to increase the contact area with the ground, thereby reducing the pressure and preventing the tires from sinking.

What happens to the pressure when the area is doubled?

Solution: When the area is doubled, the pressure is halved. They have an inverse relationship.

Why does an inflated balloon burst when a sharp object is pushed into it?

Solution: An inflated balloon bursts when a sharp object is pushed into it because the force exerted by the object creates a high pressure on the small area of the balloon, causing it to rupture.

Why are tracks of tanks made wider than regular vehicle tires?

Solution: Tracks of tanks are made wider than regular vehicle tires to distribute the weight over a larger area, reducing the pressure exerted on the ground, and preventing sinking.

How does pressure affect the boiling point of a liquid?

Solution: Pressure affects the boiling point of a liquid. As pressure increases, the boiling point of a liquid also increases, and vice versa.

Why are the blades of knives made sharp?

Solution: The blades of knives are made sharp to reduce the contact area, increasing the pressure exerted on the object being cut and making the cutting process easier.

What is the role of ball bearings in reducing friction?

Solution: Ball bearings reduce friction by providing smooth rolling contact between two moving parts, facilitating easier and smoother movement.

How does a safety pin work?

Solution: A safety pin works by using the principle of moments. The spring force applies pressure on one end, holding the clasp in place, preventing accidental opening.

Why does a cork float in water?

Solution: A cork floats in water because its density is less than that of water, causing the buoyant force to be greater than its weight.

Why does a heavier object require more force to move?

Solution: A heavier object requires more force to move because it has more mass, resulting in a greater inertial force resisting the change in motion.

Explain why we slide on a slippery surface.

Solution: We slide on a slippery surface because there is very little friction between the surfaces, allowing for an easy motion.

How does a syringe work?

Solution: A syringe works based on Pascal's law. When pressure is applied to the plunger, it creates pressure inside the syringe, forcing the liquid to be pushed out.

Why is it risky to stand under a tall tree during a lightning storm?

Solution: It is risky to stand under a tall tree during a lightning storm because the tree, being tall and projecting outwards, becomes a potential lightning conductor, increasing the risk of a lightning strike.

How does punching a hole in a can of juice help in pouring it?

Solution: Punching a hole in a can of juice allows air to enter from the hole, equalizing the pressure inside the can, resulting in a smooth and continuous flow of juice.

Why do we use a cushion while sitting?

Solution: We use a cushion while sitting to increase the contact area, reducing the pressure exerted on our body, providing a more comfortable seating experience.

State one application of hydraulic systems.

Solution: One application of hydraulic systems is in car brakes, where a small force applied to the pedal is amplified to provide greater braking force.

How does the shape of an object affect air resistance?

Solution: The shape of an object affects air resistance. Streamlined or aerodynamic shapes experience less air resistance compared to irregular shapes, allowing them to move more smoothly through the air.

Chapter 12 Friction

Q: What is friction?

A: Friction is the force that opposes the motion between two surfaces that are in contact with each other.

Q: What causes friction?

A: Friction is caused by intermolecular forces between the molecules of two surfaces in contact.

Q: How does friction affect motion?

A: Friction acts as a resistive force, slowing down or stopping the motion of objects.

Q: Name two types of friction.

A: The two types of friction are static friction and kinetic friction.

Q: Define static friction.

A: Static friction is the frictional force that prevents objects from moving when they are at rest.

Q: Define kinetic friction.

A: Kinetic friction is the frictional force that opposes the motion of objects that are already in motion.

Q: How can we increase friction between two surfaces?

A: Friction can be increased by increasing the roughness of the surfaces or by applying more force between them.

Q: How can we decrease friction between two surfaces?

A: Friction can be reduced by smoothing or lubricating the surfaces.

Q: Give an example of static friction.

A: A book placed on a table is prevented from sliding due to static friction.

Q: Give an example of kinetic friction.

A: Sliding a box across the floor creates kinetic friction between the box and the floor.

Q: What is rolling friction?

A: Rolling friction is the resistance encountered when an object rolls over a surface.

Q: Give an example of rolling friction.

A: Rolling a ball on the ground creates rolling friction between the ball and the ground.

Q: What is fluid friction?

A: Fluid friction is the resistance experienced by an object when it moves through a liquid or gas.

Q: Give an example of fluid friction.

A: Swimming through water or driving a car through air experiences fluid friction.

Q: How does friction contribute to wear and tear?

A: Friction creates heat and mechanical stress, which can lead to the wear and tear of surfaces.

Q: Why do car tires have treads on them?

A: The treads on car tires provide better traction and increase friction between the tires and the road.

Q: How does friction help us to walk?

A: Friction between our shoes and the ground prevents us from slipping, allowing us to walk.

Q: What is the importance of friction in sports activities?

A: Friction helps athletes maintain balance, change direction, and control movements during sports activities.

Q: Why do we use sandpaper to smoothen a surface?

A: Sandpaper roughens the surface by increasing friction, allowing for better adhesion of paint or glue.

Q: Why do brakes work better when they are heated?

A: Heating the brakes increases friction, allowing them to grip the wheel better and bring the vehicle to a stop.

Q: How does friction affect the efficiency of machines?

A: Friction converts useful energy into heat, reducing the efficiency of machines. 22. Q: What are the advantages of friction?

Friction enables us to walk, write, grip objects, and generate heat.

Q: What are the disadvantages of friction?

A: Friction can cause wear and tear, reduce efficiency, and impede the movement of objects.

Q: How does lubrication reduce friction?

A: Lubricants create a thin layer that separates the surfaces, reducing contact and friction between them.

Q: How does the surface area affect friction?

A: Increasing the surface area in contact increases friction.

Q: Why is it difficult to walk on a slippery surface?

A: Slippery surfaces have low friction, making it hard to maintain grip and balance.

Q: How does friction affect the speed of an object?

A: Friction opposes motion, so it reduces the speed of an object.

Q: Why do tires wear out over time?

A: Rolling friction between the tires and the road causes gradual wear and tear on the tires.

Q: How does the weight of an object affect friction?

A: Friction increases with the weight of an object. Heavier objects experience more friction.

Q: Why do we polish surfaces?

A: Polishing smoothens the surface, reducing friction and enhancing appearance.

Q: How does friction help in stopping a moving vehicle?

A: Friction between the brake pads and the wheels creates a resisting force, helping to stop the vehicle.

Q: Why do ice skaters glide smoothly on the ice?

A: Ice skaters glide smoothly due to reduced friction between the ice and the skates.

Q: What is the relationship between friction and heat generation?

A: Friction generates heat due to the conversion of mechanical energy into thermal energy.

Q: How does friction affect the efficiency of engines?

A: Friction in engines reduces their efficiency by generating heat and wasting energy.

Q: Why do some objects slide more easily on a smooth surface?

A: Smooth surfaces have less roughness, resulting in less friction and easier sliding.

Q: Explain the difference between static and kinetic friction.

A: Static friction acts on objects at rest, while kinetic friction acts on objects in motion.

Q: Why is it easier to push an object on wheels rather than dragging it?

A: Wheels reduce friction by rolling, making it easier to move an object.

Q: What is the role of oil in reducing friction?

A: Oil acts as a lubricant, forming a thin layer between surfaces and reducing friction.

Q: How does friction affect the lifespan of moving parts in machines?

A: Friction can cause wear and tear on moving parts, reducing their lifespan.

Q: Why do we use anti-skid materials on the floor?

A: Anti-skid materials increase friction, preventing slips and falls on smooth surfaces.

Q: How does surface roughness affect friction?

A: Surfaces with more roughness have higher friction due to increased interlocking between molecules.

Q: What happens to the friction between two surfaces when a lubricant is applied?

A: Friction decreases as the lubricant fills in the irregularities between the surfaces.

Q: Why do athletes use sports shoes with spikes?

A: Spiked shoes increase friction between the shoe and the ground, providing better grip and traction.

Q: How does friction help in the creation of fire?

A: Rubbing two objects creates friction, which generates heat and can ignite flammable materials.

Q: Why does a ball eventually stop rolling on a level ground?

A: Kinetic friction between the ball and the ground slows it down and eventually brings it to a stop.

Q: How does friction affect the efficiency of a bicycle chain?

A: Friction in the bicycle chain can cause energy loss and reduce pedaling efficiency.

Q: Why do car engines need oil?

A: Oil lubricates the engine components, reducing friction and preventing excessive wear.

Q: How does friction help in the braking system of a car?

A: Friction between the brake pads and the rotor creates a resisting force, slowing down the car.

Q: Why do we add wax to the surface of a snowboard?

A: Wax reduces friction between the snowboard and the snow, allowing for smoother gliding.

Q: How does friction affect the speed of a swinging pendulum?

A: Friction opposes the motion of a swinging pendulum, causing it to slow down over time.

Chapter 13 Sound

What is sound?

Solution: Sound is a form of energy that produces a sensation of hearing when it reaches our ears.

How is sound produced?

Solution: Sound is produced when an object vibrates, causing the particles in the surrounding medium to vibrate and transfer energy in the form of sound waves.

Name three sources of sound.

Solution: Three sources of sound are musical instruments, human voice, and vibrating objects such as bells.

What is the difference between sound and noise?

Solution: Sound refers to pleasant or melodic vibrations, while noise refers to unwanted or unpleasant vibrations.

Why do we hear sound better in a quiet room?

Solution: In a quiet room, there are fewer background noises that can interfere with the sound waves reaching our ears, allowing us to hear better.

Define amplitude and frequency of sound.

Solution: Amplitude refers to the maximum displacement of a particle in the medium from its rest position during the passage of a sound wave. Frequency refers to the number of complete vibrations or cycles per second.

What determines the pitch of a sound?

Solution: The pitch of a sound is determined by its frequency. Higher frequency sound waves produce high-pitched sounds, while lower frequency sound waves produce low-pitched sounds.

Explain the term 'echo.'

Solution: When sound waves bounce back after striking a reflecting surface, we hear reflected sound as an echo.

Why do we hear thunder after we see the lightning during a storm?

Solution: The speed of light is greater than the speed of sound. Hence, it takes less time for light to reach our eyes than for sound to reach our ears, causing a delay in hearing the thunder after seeing the lightning.

How does sound travel in solids?

Solution: Sound travels fastest through solids because the particles in solids are closely packed, allowing sound waves to propagate quickly.

Why does sound travel slower in gases as compared to solids?

Solution: Sound travels slower in gases because the particles in gases are widely spaced, resulting in a slower propagation of sound waves.

What is the unit of measurement for frequency?

Solution: The unit of measurement for frequency is Hertz (Hz).

Define pitch and loudness of sound.

Solution: Pitch refers to the highness or lowness of a sound. Loudness refers to the volume or intensity of a sound.

How can we increase the pitch of a sound?

Solution: Increasing the frequency of a sound wave can increase its pitch.

How can we increase the loudness of a sound?

Solution: Increasing the amplitude of a sound wave can increase its loudness.

What is the range of human hearing?

Solution: The normal range of human hearing is generally from 20 Hz to 20,000 Hz.

What is the purpose of the eardrum?

Solution: The eardrum vibrates when sound waves strike it, and these vibrations are then transmitted to the inner ear for further processing.

Name the three parts of the human ear.

Solution: The three parts of the human ear are the outer ear, middle ear, and inner ear.

Explain the working of a stethoscope.

Solution: A stethoscope amplifies the sound of the heartbeat and allows the doctor to listen to the heart by transmitting the sound waves from the patient's body to the doctor's ears.

How can you reduce noise pollution?

Solution: Noise pollution can be reduced by using earplugs, maintaining silence in sensitive areas, reducing the volume of loudspeakers, and using soundproofing materials in buildings.

What is resonance?

Solution: Resonance occurs when an object is made to vibrate at its natural frequency by absorbing energy from a sound wave of the same frequency.

What is the purpose of a soundboard in musical instruments?

Solution: The soundboard amplifies the sound produced by musical instruments and makes it louder by resonating with the vibrations of the instrument.

How does sound travel in a vacuum?

Solution: Sound cannot travel through a vacuum because it requires a medium (solid, liquid, or gas) for the particles to vibrate and carry the sound waves.

Name two animals that use echolocation to navigate and find food.

Solution: Bats and dolphins use echolocation to navigate and find food.

How does the distance of an object affect the time taken for sound to reach us?

Solution: The greater the distance of an object, the longer it takes for the sound to reach us because sound travels at a finite speed.

Explain the term 'doppler effect.'

Solution: The Doppler effect is the change in the frequency or pitch of sound waves when there is relative motion between the source of sound and the observer.

What causes a ringing sound in our ears after exposure to loud noises?

Solution: Exposure to loud noises can cause temporary damage to the tiny hair cells in our ears, resulting in a ringing sound known as tinnitus.

How does sound help bats to hunt?

Solution: Bats emit high-frequency sound waves and listen to the echoes produced when these waves bounce back from objects. By analyzing the echoes, bats can navigate and locate their prey.

Name two musical instruments that produce sound through vibrating strings.

Solution: Guitar and violin are two musical instruments that produce sound through vibrating strings.

How does the sound produced by a drum differ from that of a guitar?

Solution: The sound produced by a drum is a non-pitched sound, while a guitar produces sounds of different pitches due to the varying lengths of the vibrating strings.

What is the purpose of the tympanic membrane in the human ear?

Solution: The tympanic membrane, also known as the eardrum, vibrates when sound waves strike it, transmitting these vibrations to the inner ear.

How does noise pollution affect living organisms?

Solution: Noise pollution can lead to sleep disturbances, stress, hearing loss, and other health issues in living organisms exposed to excessive noise levels.

Why does sound travel faster on a hot summer day compared to a cold winter day?

Solution: Sound travels faster on a hot summer day because the particles in the air move faster due to higher temperature, allowing for quicker transmission of sound waves.

What is the purpose of the cochlea in the human ear?

Solution: The cochlea converts sound vibrations into electrical signals that are then sent to the brain for interpretation.

Explain the concept of an ultrasonic sound.

Solution: Ultrasonic sound refers to sound waves with frequencies higher than the upper limit of human hearing (20,000 Hz). These sounds are used in various applications like sonar, medical imaging, and pest control.

What is a sound wave, and how is it represented?

Solution: A sound wave is a pattern of vibrations that travels through a medium. It is represented graphically using a waveform, with the y-axis representing the amplitude and the x-axis representing time.

How does the medium affect the speed of sound?

Solution: The speed of sound varies depending on the medium through which it travels. Sound travels fastest through solids, followed by liquids, and slowest through gases.

What are the uses of an oscilloscope in the study of sound?

Solution: An oscilloscope helps in visualizing and measuring sound waves, demonstrating concepts like frequency, amplitude, and waveforms.

How can we reduce noise-induced hearing loss?

Solution: We can reduce noise-induced hearing loss by wearing ear protection, limiting exposure to loud noises, and keeping volume levels at a comfortable level while using headphones or earphones.

Explain the concept of sympathetic resonance.

Solution: Sympathetic resonance occurs when an object vibrates at the natural frequency of another object, causing the second object to vibrate or produce sound without direct contact.

What is an ultrasonic cleaner, and how does it work?

Solution: An ultrasonic cleaner uses high-frequency sound waves to create tiny bubbles that implode and produce intense vibrations, effectively cleaning delicate objects like jewelry or surgical instruments.

How does sound help us recognize the distance and direction of an approaching vehicle?

Solution: Sound waves emitted by an approaching vehicle reach our ears sooner when the vehicle is closer, allowing us to judge its distance and direction.

What is the purpose of a soundproof room?

Solution: A soundproof room is designed to prevent sound from entering or leaving, ensuring a quiet environment within or minimizing external noise pollution.

How does the ear protect itself from loud sounds?

Solution: When exposed to loud sounds, the ear has a mechanism to protect itself by reflexively contracting muscles, which reduces the transmission of vibrations to the inner ear.

Explain the concept of frequency modulation (FM) in radio broadcasting.

Solution: Frequency modulation is a process in which the frequency of the carrier wave is varied according to the amplitude of the sound wave, resulting in high-quality sound transmission in FM radios.

What is the relationship between the wavelength and frequency of a sound wave?

Solution: The wavelength of a sound wave is inversely proportional to its frequency. Higher-frequency sound waves have shorter wavelengths, and lowerfrequency sound waves have longer wavelengths.

How is sound used in medical diagnosis, such as ultrasound imaging?

Solution: Ultrasound imaging uses high-frequency sound waves to create images of organs and tissues inside the body, aiding in medical diagnosis without harmful radiation.

What is the function of the semicircular canals in the human ear?

Solution: The semicircular canals are responsible for maintaining our sense of balance and detecting rotational movements of the head.

How does sound help in detecting cracks or faults in machinery?

Solution: Sound analysis can help detect cracks or faults in machinery by listening for abnormal or irregular sounds produced by the equipment, indicating potential issues.

What is the role of sound engineers in music recordings?

Solution: Sound engineers are responsible for recording, mixing, and mastering music, ensuring optimal sound quality and balance in recorded tracks.

Chapter 14 Chemical Effects of Electric Current

What is an electric current?

- An electric current is the flow of electric charge in a circuit.

What are conductors?

- Conductors are materials that allow electric current to pass through them easily.

Give some examples of good conductors.

- Copper, aluminum, and silver are examples of good conductors.

What are insulators?

- Insulators are materials that do not allow electric current to pass through them easily.

Give some examples of insulators.

- Rubber, plastic, and wood are examples of insulators.

What happens when an electric current passes through a conductor?

- The conductor can get heated up or produce light, depending on the conditions.

What is electrolysis?

- Electrolysis is a chemical process that involves the breakdown of substances using electricity.

Explain the process of electrolysis.

- When an electric current is passed through an electrolyte, chemical reactions occur at the electrodes, resulting in the formation of new substances.

What are electrodes?

- Electrodes are conductors that are used to make contact with an electrolyte.

Define the terms anode and cathode. - The anode is the positively charged electrode, and the cathode is the negatively charged electrode.

What are the effects of electrolysis?

- The effects of electrolysis include the decomposition of molecules, the formation of new substances, and the release of gases.

What happens during electrolysis of water?

- During electrolysis of water, hydrogen gas is liberated at the cathode, and oxygen gas is liberated at the anode.

Which substance is usually used as an electrolyte in the electrolysis of water?

- Dilute sulfuric acid is commonly used as an electrolyte in the electrolysis of water.

What is electroplating?

- Electroplating is a process in which a thin layer of metal is deposited on an object using the principle of electrolysis.

State two uses of electroplating.

- Electroplating is used to make objects corrosion-resistant and enhance their appearance.

What is a cell?

- A cell is a device that converts chemical energy into electrical energy.

Name the two types of cells.

- The two types of cells are primary cells (non-rechargeable) and secondary cells (rechargeable).

Give an example of a primary cell.

- A common example of a primary cell is the dry cell used in household batteries.

Give an example of a secondary cell.

- A lead-acid battery used in automobiles is an example of a secondary cell.

What is corrosion?

- Corrosion is the process of deterioration or damage to a metal due to its reaction with substances in the environment.

How can the rate of corrosion be minimized?

- The rate of corrosion can be minimized by applying a coating of paint, oil, or grease on the metal surface, or by galvanizing or electroplating it.

What is an electrochemical cell?

- An electrochemical cell is a device that converts chemical energy into electrical energy through redox reactions.

Explain the working of an electrochemical cell.

- An electrochemical cell consists of two electrodes (anode and cathode) immersed in an electrolyte solution. Chemical reactions occur at the electrodes, generating a flow of electrons, which results in the production of electrical energy.

What is the difference between an electric circuit and an electrochemical cell?

- An electric circuit is a closed path through which electric current flows, while an electrochemical cell is a specific type of energy conversion device.

Define the terms open circuit and closed circuit.

- An open circuit does not allow the flow of electric current, while a closed circuit provides a continuous path for electric current to flow.

State Ohm's law.

- Ohm's law states that the current flowing through a conductor is directly proportional to the voltage applied, given the resistance remains constant.

What are the units of electric current, voltage, and resistance?

- The unit of electric current is ampere (A), voltage is measured in volts (V), and resistance is measured in ohms (?).

What happens if the resistance in a circuit increases?

- If the resistance in a circuit increases, the current flowing through the circuit decreases, provided the voltage remains constant.

What is meant by the term short circuit?

- A short circuit occurs when a circuit's resistance becomes very low, allowing a large amount of current to flow uncontrollably.

Why is it important to use proper fuses in electrical circuits?

- Proper fuses in electrical circuits protect the circuit by breaking the flow of current during a fault or short circuit, preventing damage or accidents.

What is a chemical cell?

- A chemical cell is a device that converts chemical energy into electrical energy through a redox reaction.

Give an example of a chemical cell.

- A common example of a chemical cell is the zinc-carbon dry cell used in portable electronic devices.

What is the importance of grounding electrical appliances?

- Grounding electrical appliances ensures that excessive electric charge is safely directed to the ground, protecting people and preventing damage to appliances.

What are the safety precautions one should follow while handling electrical appliances?

- Avoid touching electrical appliances with wet hands, unplug appliances before cleaning, use proper insulation, and never overload electrical circuits.

How can we differentiate between conductors and insulators?

- Conductors allow electric current to pass through easily, while insulators do not.

Explain the difference between an open circuit and a closed circuit with an example.

- In an open circuit, the path for electric current is broken, and no current flows. In contrast, a closed circuit provides a complete path for current to flow, allowing it to pass through various components.

What is the role of electrolytes in an electrochemical cell?

- Electrolytes allow the movement of charged particles (ions) within the cell, which plays a crucial role in the chemical reactions occurring at the electrodes.

How does electroplating prevent objects from corrosion?

- Electroplating with a layer of a non-corrosive metal like chromium or zinc prevents direct contact of the object with the corrosive environment, protecting it from corrosion.

Explain the principle behind a primary cell.

- Primary cells work on the principle of an irreversible chemical reaction, where reactants are consumed, leading to the depletion of stored chemical energy and termination of the cell's ability to produce electricity.

What is the purpose of a salt bridge in an electrochemical cell?

- A salt bridge maintains electrical neutrality in an electrochemical cell by allowing the flow of ions to balance the charge between the two half-cells.

How does the size of an electrode affect the rate of electrolysis?

- The rate of electrolysis increases with an increase in the surface area of the electrodes as larger electrodes provide more contact points for the chemical reactions to occur.

Explain why metals like gold and platinum are used as electrodes in electrolysis.

- Metals like gold and platinum do not react easily with the substances present in the electrolyte, ensuring that the electrode material remains stable during the process of electrolysis.

State the chemical reactions occurring during the electrolysis of water.

- At the cathode: 2H+ + 2e^- ? H2 (hydrogen gas is liberated) At the anode: 4OH^- ? 2H2O + O2 + 4e^- (oxygen gas is liberated)

How does the use of an LED bulb prevent overheating in a circuit?

- LED bulbs are energy-efficient and do not produce excessive heat compared to conventional incandescent bulbs, reducing the chances of overheating in a circuit.

What precautions should be taken while handling electrolytes used in an electrochemical cell?

- Wear protective gloves and goggles, avoid ingesting electrolytes, and handle them with care as some electrolytes can be corrosive or toxic.

Define the term electric potential.

- Electric potential is the amount of electric potential energy per unit charge possessed by a point in an electric circuit.

How is electricity produced in a hydroelectric power plant?

- In a hydroelectric power plant, electricity is generated by converting the potential energy of falling water into electrical energy using turbines and generators.

What is the purpose of a switch in an electric circuit?

- A switch is used to control the flow of electric current in a circuit by either completing or breaking the circuit.

Which type of cell is commonly used in wristwatches and calculators?

- Button cells (small-sized primary cells) are commonly used in wristwatches and calculators due to their compact size and longer shelf life.

Why is it important to avoid mixing different electrolytes in an electrochemical cell?

- Mixing different electrolytes can lead to unwanted chemical reactions and unpredictable results, affecting the performance and stability of the cell.

Chapter 15 Some Natural Phenomena

Q: What is lightning?

A: Lightning is the sudden discharge of static electricity between clouds and the Earth, or between different parts of clouds.

Q: How is lightning formed?

A: Lightning is formed when positively charged particles in the atmosphere collide with negatively charged particles, creating an imbalance that results in a discharge.

Q: What causes thunder?

A: Thunder is caused by the rapid expansion and contraction of air surrounding a lightning bolt, creating a shockwave that we hear as thunder.

Q: What is an earthquake?

A: An earthquake is the shaking of the Earth's surface caused by the sudden release of energy in the Earth's crust, resulting in seismic waves.

Q: How are earthquakes measured?

A: Earthquakes are measured using instruments called seismographs and the magnitude scale called Richter scale.

Q: Which instrument is used to detect and measure earthquakes?

A: Seismographs are used to detect and measure earthquakes.

Q: Define the term 'tornado.'

A: A tornado is a rapidly rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud.

Q: What is the difference between a cyclone and a tornado?

A: A cyclone is a large-scale weather system that forms over water, while a tornado is a localized and smaller-scale rotary system that forms over land.

Q: Explain the concept of a rainbow.

A: A rainbow is a natural phenomenon that occurs when sunlight is refracted, reflected, and dispersed in water droplets in the air, creating a spectrum of colors.

Q: Define the term 'tsunami.'

A: A tsunami is a series of enormous ocean waves caused by underwater earthquakes, volcanic eruptions, or landslides.

Q: How are clouds formed?

A: Clouds are formed when warm, moist air rises and cools down, leading to the condensation of water vapor into tiny water droplets or ice crystals.

Q: What are the different types of clouds?

A: The different types of clouds include cumulus clouds, stratus clouds, and cirrus clouds.

Q: Explain the concept of rainfall.

A: Rainfall occurs when water droplets in clouds combine and become too heavy to be supported by air currents, falling to the ground due to gravity.

Q: What is the water cycle?

A: The water cycle is the continuous movement of water on Earth, including evaporation, condensation, precipitation, and runoff.

Q: How does a thunderstorm occur?

A: A thunderstorm occurs when there is an atmospheric instability, typically involving warm air rising rapidly, creating cumulonimbus clouds, thunder, and lightning.

Q: What is the role of wind in the formation of cyclones?

A: Wind is one of the key factors in the formation of cyclones. It helps intensify cyclones by supplying warm, moist air and driving their rotational movement.

Q: Define the term 'hurricane.'

A: A hurricane is a large, powerful, and intense tropical storm with strong winds and heavy rainfall, forming over warm ocean waters.

Q: How does a volcanic eruption occur?

A: A volcanic eruption occurs when molten rock, ash, and gases are expelled from a volcano due to pressure buildup in the Earth's crust.

Q: Explain the concept of a landslide.

A: A landslide happens when a mass of soil, rock, or debris slides down a slope, often triggered by excessive rainfall, earthquakes, or human activities.

Q: What is the cause of auroras?

A: Auroras, also known as the Northern or Southern Lights, occur when charged particles from the Sun collide with Earth's atmosphere, creating colorful light displays.

Q: How are tornadoes formed?

A: Tornadoes are formed when warm, moist air from the ground meets colder, drier air in the atmosphere, resulting in the formation of a rotating column of air.

Q: What is the role of lightning rods in protecting buildings from lightning strikes?

A: Lightning rods are metal rods installed on buildings that provide a safe pathway for lightning to travel, directing it to the ground and reducing the risk of property damage.

Q: How do seismographs work?

A: Seismographs contain a weight suspended on a spring or pendulum, which moves during an earthquake, and this movement is recorded on a rotating drum or a digital sensor.

Q: What precautions should be taken during an earthquake?

A: During an earthquake, it is essential to stay calm, take cover under a sturdy piece of furniture, or stay in an open space away from tall objects that may fall.

Q: What is the role of the Richter scale in measuring earthquakes?

A: The Richter scale measures the energy released by an earthquake, ranging from 0 to 10, with each increment representing a tenfold increase in the magnitude of the earthquake.

Q: How can we stay safe during a thunderstorm?

A: To stay safe during a thunderstorm, avoid open areas, tall objects, metal objects, and water bodies. Seek shelter indoors or in a hard-topped vehicle.

Q: What is the significance of earthquake-resistant constructions?

A: Earthquake-resistant constructions are designed to withstand the lateral forces and vibrations produced by earthquakes, ensuring the safety of the occupants.

Q: How does lightning pose a threat to humans?

A: Lightning can pose a threat to humans as it can cause severe electric shocks, burns, or even fatalities. It is important to seek shelter during thunderstorms.

Q: What safety measures can be followed during a cyclone?

A: Safety measures during a cyclone include staying indoors, away from windows, following evacuation orders, and having emergency supplies such as food, water, and first aid kits.

Q: Explain the role of the ozone layer in protecting the Earth.

A: The ozone layer protects the Earth's surface by absorbing the majority of the Sun's ultraviolet (UV) radiation, preventing it from reaching the Earth's surface.

Q: How can we predict and track hurricanes?

A: Meteorologists use satellites, weather radar, and historical data to predict and track hurricanes, helping to issue timely warnings and evacuation orders.

Q: What leads to the formation of a thundercloud?

charges.

Q: How can we protect ourselves from a tsunami?

A: To protect oneself from a tsunami, it is advisable to move to higher ground, away from the coast, upon hearing a tsunami warning. Follow evacuation procedures if instructed.

Q: What is the relationship between earthquakes and tsunamis?

A: Earthquakes, particularly those occurring underwater, have the potential to generate tsunamis due to the displacement of large volumes of water.

Q: How is the energy generated by lightning used by living organisms?

A: The energy generated by lightning helps convert atmospheric nitrogen into a form that can be absorbed by plants for their growth and development.

Q: Define the term 'drought.'

A: A drought is a prolonged period of abnormally dry weather, resulting in a shortage of water supply for agriculture, ecosystems, and human consumption.

Q: Explain the concept of a heatwave.

A: A heatwave is a period of excessively hot weather, often accompanied by high humidity, leading to increased discomfort, health risks, and heat-related illnesses.

Q: How can we reduce the impact of lightning strikes on power systems?

A: Lightning protection systems, grounding measures, and surge protectors can help reduce the impact of lightning strikes on power systems, preventing damage and power outages.

Q: What is the relationship between air pressure and wind?

A: Differences in air pressure contribute to the formation of wind. Air moves from areas of high pressure to areas of low pressure, creating wind patterns.

Q: Explain the concept of a dust storm.

A: Dust storms occur when strong winds lift and carry large amounts of dry soil or sand particles, reducing visibility and causing potential health hazards.

Q: What precautions should be taken during a volcanic eruption?

A: During a volcanic eruption, it is important to follow evacuation orders, wear masks to prevent inhaling ash, and protect oneself from falling debris and pyroclastic flows.

Q: How do monsoons impact the agricultural sector?

A: Monsoons play a crucial role in the agricultural sector as they provide much-needed rainfall for crop cultivation, replenishing water sources, and supporting overall food production.

Q: What is the role of lightning in the nitrogen cycle?

A: Lightning helps fix atmospheric nitrogen, converting it into a form usable by plants through a process called nitrogen fixation, contributing to soil fertility.

Q: How can we detect the approach of a cyclone in advance?

A: Advanced weather monitoring systems, satellite imagery, and Doppler radar help detect the approach of a cyclone in advance, enabling timely warnings and necessary preparations.

Q: What causes the phenomenon of a solar eclipse?

A: A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting a shadow on the Earth and blocking the sunlight from reaching specific regions.

Q: How can we measure the speed and direction of wind?

A: Anemometers are used to measure the speed of wind, while wind vanes or weather vanes are used to determine the direction from which the wind is blowing.

Q: What are the safety measures to be taken during a volcanic eruption?

A: Safety measures during a volcanic eruption include following evacuation orders, covering the nose and mouth with a damp cloth to breathe, and protecting oneself from falling ash and gases.

Q: Why are tornadoes more frequent in certain regions, like Tornado Alley?

A: Certain regions, like Tornado Alley in the United States, experience more tornadoes due to specific atmospheric conditions, including the convergence of warm, humid air and cold, dry air masses.

Q: How do earthquakes affect buildings and structures?

A: Earthquakes can cause severe damage to buildings and structures due to ground shaking, ground displacement, or liquefaction, highlighting the importance of earthquake-resistant designs.

Q: What causes the phenomenon of a lunar eclipse?

A: A lunar eclipse occurs

Chapter 16 Light

What is light?

- Light is a form of energy that enables us to see objects.

What are luminous objects?

- Luminous objects are those that produce their own light, such as the Sun or a light bulb.

What are non-luminous objects?

- Non-luminous objects are objects that do not produce their own light, such as books or tables.

What is the speed of light?

- The speed of light is approximately 3 × 10^8 meters per second.

Define reflection of light.

- Reflection is the bouncing back of light when it strikes the surface of an object, like in a mirror.

What is a mirror?

- A mirror is a smooth, shiny surface that can reflect light.

What are the different types of mirrors?

- The two main types are concave and convex mirrors.

What is refraction?

- Refraction is the bending of light when it travels from one medium to another, like when light passes through water.

What causes a rainbow?

- A rainbow is caused by the refraction, dispersion, and reflection of sunlight in water droplets in the atmosphere.

How does a lens work?

- A lens is a transparent object that refracts light to form an image. It can be converging (convex) or diverging (concave).

What is the difference between a convex and concave lens?

- A convex lens is thicker in the middle and converges light, while a concave lens is thinner in the middle and diverges light.

What is the focal length of a lens?

- The focal length is the distance between the lens and the point where parallel rays of light converge or diverge.

What is the difference between a real and virtual image?

- A real image can be formed on a screen, while a virtual image cannot.

What is dispersion of light?

- Dispersion of light is the splitting of white light into its component colors, seen in a prism.

How does a periscope work?

- A periscope uses multiple reflections to see objects that are not directly visible.

Why is the sky blue?

- The sky appears blue because of the scattering of sunlight by the gases and particles in the Earth's atmosphere.

What is total internal reflection?

- Total internal reflection occurs when light traveling through a dense medium is totally reflected back into the same medium.

What is the critical angle?

- The critical angle is the angle of incidence that produces an angle of refraction of 90 degrees.

What is the spectrum of light?

- The spectrum of light is the range of colors produced when white light is dispersed, consisting of red, orange, yellow, green, blue, indigo, and violet.

How does a camera work?

- A camera uses a lens to focus light onto a light-sensitive material, capturing an image.

What is fluorescence?

- Fluorescence is the emission of light of a longer wavelength after absorbing light of a shorter wavelength.

How does a magnifying glass work?

- A magnifying glass uses a convex lens to create a larger, magnified image of an object.

What is an optical fiber?

- An optical fiber is a thin, flexible, transparent fiber that can transmit light signals over long distances using the principle of total internal reflection.

How does night vision work?

- Night vision devices use special technology to amplify existing light and make objects visible in the dark.

What is an eclipse?

- An eclipse occurs when one celestial body, such as the Moon or the Sun, partially or completely blocks the light from another celestial body.

How does a telescope work?

- A telescope uses a combination of lenses and mirrors to gather and focus light, enabling us to view distant objects in space.

What are the primary colors of light?

- The primary colors of light are red, green, and blue.

What is the law of reflection?

- The law of reflection states that the angle of incidence is equal to the angle of reflection when light reflects off a surface.

What is the role of a filter in light?

- A filter selectively transmits certain colors of light while absorbing or blocking others.

What is the difference between a transparent, translucent, and opaque object?

- A transparent object allows all light to pass through, a translucent object allows some light to pass through but scatters it, and an opaque object does not allow any light to pass through.

Explain the working principle of a periscope.

- A periscope consists of two mirrors set at an angle. Light enters through one end, reflects off the mirrors, and allows the viewer to see objects that are not directly visible.

How does a microscope work?

- A microscope uses a combination of lenses to magnify small objects that are not visible to the naked eye.

Why does a pencil appear bent when placed in a glass of water?

- When light passes from air into water, it changes direction due to refraction, making the pencil appear bent.

What is the difference between a convex and a concave mirror?

- A convex mirror curves outward and forms a smaller, virtual image, while a concave mirror curves inward and can form both real and virtual images.

How does a rainbow form after rainfall?

- When sunlight passes through raindrops, it gets refracted, reflected, and dispersed, creating a rainbow.

What is the function of a lens in the human eye?

- The lens in the human eye helps to focus incoming light onto the retina, forming clear images.

Explain the concept of critical angle in optics.

- The critical angle is the minimum angle of incidence beyond which light traveling through a denser medium gets totally reflected.

Why do objects in a room appear to have color under white light?

- Under white light, objects absorb some colors and reflect others, giving them their perceived color.

What are the uses of concave and convex lenses?

- Convex lenses are used in magnifying glasses, cameras, and telescopes, while concave lenses are used in glasses for correcting nearsightedness.

How does a solar panel convert sunlight into electricity?

- Solar panels contain photovoltaic cells that absorb sunlight and convert it into electricity through a reaction with semiconductor materials.

What causes stars to twinkle?

- The twinkling of stars is caused by the bending and scattering of light as it passes through the Earth's atmosphere.

How does a prism work?

- A prism refracts white light, separating it into its component colors by different amounts, creating a spectrum.

What is the difference between regular and diffuse reflection?

- Regular reflection occurs when light reflects off a smooth surface, while diffuse reflection occurs when light reflects off a rough or uneven surface.

How does a laser work?

- A laser emits a focused beam of light through a process called stimulated emission of radiation.

What are the different colors of light seen in a rainbow?

- The colors in a rainbow are red, orange, yellow, green, blue, indigo, and violet (ROYGBIV).

What is the role of a converging lens?

- A converging lens brings divergent light rays together to form a real or virtual image.

How does a prism produce a spectrum?

- A prism refracts different colors of light at different angles, separating white light into its component colors.

What is the angle of incidence?

- The angle of incidence is the angle between an incident ray of light and the normal, or perpendicular, to a surface it strikes.

What is the principal focus of a lens?

- The principal focus of a lens is the point where parallel rays of light converge or appear to diverge after passing through the lens.

Why does a mirage occur?

- A mirage occurs due to the phenomenon of total internal reflection, where light rays bend when passing through air layers of different temperatures, creating an illusion of water or images.

Chapter 17 Stars and the Solar System

Question: What is the Sun?

Solution: The Sun is a star, and it is the closest star to Earth.

Question: What are stars made of?

Solution: Stars are mostly composed of gases, primarily hydrogen and helium.

Question: Why does the Sun appear to shine?

Solution: The Sun shines because of the nuclear fusion reactions occurring in its core.

Question: What is a solar system?

Solution: A solar system consists of a star, such as our Sun, and the celestial bodies orbiting around it, like planets, moons, asteroids, and comets.

Question: Name the eight planets of our solar system in order.

Solution: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Question: What is a planet?

Solution: A planet is a celestial body that orbits around a star, is spherical in shape, and has cleared its orbit of other debris.

Question: Which is the largest planet in our solar system?

Solution: Jupiter is the largest planet in our solar system.

Question: Which is the smallest planet in our solar system?

Solution: Mercury is the smallest planet in our solar system.

Question: What is a satellite?

Solution: A satellite is a celestial body that orbits around a planet. For example, Earth has one natural satellite called the Moon.

Question: What is a comet?

Solution: A comet is a small celestial object made of ice, dust, and rock that orbits the Sun. When a comet gets closer to the Sun, it develops a glowing head and sometimes a tail.

Question: What is a meteoroid?

Solution: A meteoroid is a small rock or object traveling through space. When it enters Earth's atmosphere and burns up, it is called a meteor.

Question: What is a constellation?

Solution: A constellation is a group of stars that are named and connected to form a recognizable pattern or shape.

Question: What is the Milky Way?

Solution: The Milky Way is the spiral-shaped galaxy in which our solar system is located.

Question: What causes day and night on Earth?

Solution: The rotation of the Earth on its axis causes day and night.

Question: What causes the seasons on Earth?

Solution: The tilt of the Earth's axis causes the changing seasons on Earth.

Question: Why do stars appear to move across the sky?

Solution: The rotation of the Earth makes the stars appear to move across the sky.

Question: Why do some stars appear brighter than others?

Solution: Stars appear brighter either because they are closer to Earth or because they are intrinsically more luminous.

Question: What is a constellation map?

Solution: A constellation map is a diagram that shows the positions of constellations in the sky.

Question: How are stars formed?

Solution: Stars are formed from large clouds of gas and dust called nebulae. Gravity causes the nebulae to collapse and form stars.

Question: What is a light-year?

Solution: A light-year is the distance traveled by light in one year. It is used to measure vast distances in space.

Question: What is a black hole?

Solution: A black hole is a region in space where gravity is so strong that nothing, not even light, can escape its pull.

Question: What is a supernova?

Solution: A supernova is a massive explosion that occurs when a star reaches the end of its life cycle.

Question: What is the difference between a planet and a dwarf planet?

Solution: A dwarf planet is a celestial body that shares some characteristics of a planet but has not cleared its orbit of other debris.

Question: How do astronomers classify stars?

Solution: Astronomers classify stars based on their color, temperature, size, and brightness.

Question: What is a solar eclipse?

Solution: A solar eclipse occurs when the Moon passes between the Earth and the Sun, causing the Sun to be temporarily blocked.

Question: What is a lunar eclipse?

Solution: A lunar eclipse occurs when the Earth passes between the Sun and the Moon, causing the Moon to be temporarily blocked.

Question: What is the purpose of a space probe?

Solution: Space probes are sent into space to gather information about celestial bodies, including planets, moons, and comets.

Question: What is the Hubble Space Telescope?

Solution: The Hubble Space Telescope is a powerful telescope placed in space to capture clear images of distant objects in the universe.

Question: What is the importance of studying stars and the solar system?

Solution: Studying stars and the solar system helps us understand the vastness and workings of the universe, as well as our place in it.

Question: How do stars produce energy?

Solution: Stars produce energy by nuclear fusion, where hydrogen atoms fuse to form helium, releasing tremendous amounts of energy in the process.

Question: What is the significance of the Sun for life on Earth?

Solution: The Sun provides us with heat, light, and energy. It is essential for life on Earth.

Question: How are planets different from stars?

Solution: Planets do not produce their own light and are much smaller than stars. They revolve around stars, while stars emit light and heat.

Question: Which planet has the most moons?

Solution: Jupiter has the most moons in our solar system, with over 79 known moons.

Question: What are the asteroid belts?

Solution: The asteroid belt is a region between Mars and Jupiter where numerous asteroids orbit the Sun.

Question: How do scientists measure the distance to stars?

Solution: Scientists use a unit called a parsec or light-years to measure the distance to stars.

Question: What is a star cluster?

Solution: A star cluster is a group of stars that are close together and believed to have formed from the same gas cloud.

Question: Name two famous constellations.

Solution: Orion and Ursa Major (the Big Dipper) are two famous constellations.

Question: What is the difference between a meteor and a meteorite?

Solution: A meteor is a meteoroid entering Earth's atmosphere and burning up, while a meteorite is a meteoroid that survives the journey through the atmosphere and reaches the Earth's surface.

Question: Can a comet collide with Earth?

Solution: While it is rare, comets can potentially collide with Earth, but most burn up in the atmosphere.

Question: How long does it take for Earth to orbit the Sun once?

Solution: Earth takes approximately 365.25 days to orbit the Sun once, resulting in a leap year every four years.

Question: What is the difference between a waxing and waning moon?

Solution: A waxing moon describes the moon's illumination increasing, while a waning moon describes the moon's illumination decreasing.

Question: What determines the color of a star?

Solution: The color of a star is determined by its temperature, with hotter stars appearing bluish-white and cooler stars appearing reddish.

Question: What is the Oort cloud?

Solution: The Oort cloud is a hypothetical region located far beyond our solar system that is believed to contain a vast number of comets.

Question: Which planet is known as the "Red Planet"?

Solution: Mars is known as the "Red Planet" due to its reddish appearance caused by iron oxide (rust) on its surface.

Question: What is the closest star to Earth (besides the Sun)?

Solution: The closest star to Earth (besides the Sun) is Proxima Centauri, which is part of the Alpha Centauri star system.

Question: What is a light spectrum?

Solution: A light spectrum is a band of colors obtained when white light passes through a prism or diffracts through a grating.

Question: What is an exoplanet?

Solution: An exoplanet is a planet that orbits a star outside of our solar system.

Question: What is the significance of the North Star or Polaris?

Solution: Polaris is a bright star that remains almost stationary in the sky and helps in navigation as it aligns with the Earth's axis of rotation, making it useful for determining directions.

Question: How old is the universe?

Solution: The universe is estimated to be around 13.8 billion years old based on scientific evidence.

Question: What is the purpose of a space station?

Solution: A space station serves as a base for astronauts to live and conduct experiments in space. It also acts as a platform for observing and researching the universe.

Chapter 18 Pollution of Air and Water

What is pollution?

Solution: Pollution refers to the introduction of harmful substances or contaminants into the environment that cause adverse effects on living organisms or the natural environment.

Define air pollution.

Solution: Air pollution is the contamination of the air by various harmful substances, including gases, particulate matter, and biological materials, which can be detrimental to human health and the environment.

List some sources of air pollution.

Solution: Some common sources of air pollution include vehicle emissions, industrial activities, fossil fuel combustion, agricultural practices, and waste burning.

How does burning of fossil fuels contribute to air pollution?

Solution: Burning fossil fuels releases pollutants such as carbon dioxide, sulfur dioxide, nitrogen oxides, and particulate matter, which contribute to air pollution and the greenhouse effect.

What is smog?

Solution: Smog is a type of air pollution that occurs when pollutants, especially from vehicle emissions and industrial activities, react with sunlight and form a haze-like mixture of harmful gases and particulate matter.

How does air pollution affect human health?

Solution: Air pollution can cause respiratory problems, allergies, cardiovascular diseases, and even lung cancer in humans. It can also exacerbate existing respiratory conditions like asthma.

What causes water pollution?

Solution: Water pollution is caused by the contamination of water bodies, such as rivers, lakes, and oceans, due to the discharge of pollutants like industrial waste, sewage, agricultural chemicals, and oil spills.

Why is it important to conserve water?

Solution: Conserving water is essential to ensure its availability for future generations. Water scarcity can occur due to pollution, overuse, and climate change, so conservation helps maintain the balance of our ecosystems.

Explain the term 'eutrophication.'

Solution: Eutrophication is the excessive growth of algae and other aquatic plants in water bodies, caused by the presence of high nutrient levels, mainly nitrogen and phosphorus. This leads to oxygen depletion, harming aquatic life.

What are the effects of water pollution on marine life?

Solution: Water pollution can lead to the death of marine organisms, disruption of aquatic ecosystems, harmful algal blooms, and the bioaccumulation of toxic substances in fish, which can then harm humans who consume them.

How can we reduce air pollution caused by vehicles?

Solution: To reduce vehicle emissions, we can promote the use of public transportation, carpooling, walking, or cycling. Additionally, adopting electric vehicles and maintaining proper vehicle maintenance can help minimize air pollution.

Discuss ways to reduce water pollution at home.

Solution: To reduce water pollution at home, we should avoid the improper disposal of hazardous household chemicals, limit the use of fertilizers and pesticides in gardening, and properly manage and dispose of waste and sewage.

What is the greenhouse effect?

Solution: The greenhouse effect is a natural process that occurs when Earth's atmosphere traps heat from the sun, leading to a rise in temperature. However, human activities have significantly intensified this effect, causing global warming.

What are the major greenhouse gases?

Solution: The major greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases, which trap heat in the atmosphere and contribute to global warming and climate change.

How does deforestation contribute to air pollution?

Solution: Deforestation leads to a reduction in the number of trees that absorb carbon dioxide. As a result, there is excess carbon dioxide in the atmosphere which contributes to global warming and air pollution.

Explain the concept of "reduce, reuse, recycle" in waste management.

Solution: "Reduce, reuse, recycle" is a principle that encourages minimizing waste generation, finding alternative uses for items before discarding them, and promoting the recycling of materials to conserve resources and reduce pollution.

What measures can be taken to control water pollution caused by industrial waste?

Solution: Industries should treat their waste before releasing it into water bodies, implement and follow proper waste management practices, and use ecofriendly technologies to minimize the release of harmful pollutants.

How does thermal pollution affect aquatic ecosystems?

Solution: Thermal pollution occurs when there is a significant increase in the temperature of water bodies due to industrial activities or power generation. This rise in temperature reduces oxygen levels, harming aquatic organisms and upsetting the balance of the ecosystem.

Explain the role of wetlands in water pollution control.

Solution: Wetlands act as natural filters and can effectively remove pollutants from water. They absorb excess nutrients like nitrogen and phosphorus and help mitigate the impacts of water pollution, enhancing water quality.

Describe the impact of noise pollution on human health.

Solution: Noise pollution can lead to stress, hearing loss, sleep disturbances, and interference with communication and concentration. Prolonged exposure to high levels of noise can also cause cardiovascular problems.

How can individuals contribute to reducing air pollution?

Solution: Individuals can reduce air pollution by conserving energy, using clean and renewable energy sources, planting trees, reducing vehicle usage, and promoting awareness regarding air pollution's harmful effects.

Discuss the renewable sources of energy that can reduce air pollution.

Solution: Renewable sources of energy such as solar, wind, hydro, and geothermal power do not emit harmful pollutants during electricity generation, thus reducing air pollution caused by fossil fuel combustion.

Explain the concept of a 'carbon footprint' related to air pollution.

Solution: A carbon footprint is the total amount of greenhouse gases, mainly carbon dioxide, released into the atmosphere as a result of human activities. It provides an estimate of an individual's or organization's contribution to global warming and air pollution.

How does water pollution affect agriculture?

Solution: Water pollution can contaminate irrigation water, reducing crop yield and quality. It can also harm livestock if they consume polluted water. Longterm exposure to water contaminated with agricultural chemicals can lead to soil degradation and ecological imbalances.

Discuss the impact of plastic pollution on aquatic life.

Solution: Plastic pollution in water bodies can cause entanglement and ingestion risks for marine animals. They can suffocate or starve due to plastic debris blocking their digestive systems. It disrupts the marine food chain and leads to the death of many marine species.

What are the health hazards of drinking polluted water?

Solution: Drinking polluted water can lead to various waterborne diseases like cholera, typhoid, dysentery, and hepatitis. It can also cause stomach infections, diarrhea, and other gastrointestinal disorders.

What steps can be taken to purify drinking water?

Solution: Drinking water can be purified through processes like boiling, using water filters or purifiers, and using chlorine or iodine tablets. Municipalities also treat drinking water through processes like filtration and disinfection.

How does air pollution affect the ozone layer?

Solution: Some air pollutants, such as chlorofluorocarbons (CFCs), contribute to the depletion of the ozone layer. This results in the thinning of the ozone layer in the stratosphere, which increases the harmful ultraviolet (UV) radiation reaching the Earth's surface.

Explain the role of the government in controlling air and water pollution.

Solution: Governments play a crucial role in regulating and enforcing laws and regulations related to air and water pollution. They establish emission standards, monitor pollution levels, and enforce penalties for non-compliance to enforce environmental protection.

Discuss the consequences of water pollution on tourism.

Solution: Water pollution negatively impacts tourist destinations by reducing the aesthetic appeal of water bodies, causing beach closures due to contaminated water, and damaging marine ecosystems, discouraging tourists and affecting local economies.

What is the impact of air pollution on the ozone layer?

Solution: While air pollution predominantly affects the quality of air we breathe, certain pollutants like CFCs can reach the upper atmosphere and harm the ozone layer, resulting in the thinning of this protective shield.

How does indoor air pollution differ from outdoor air pollution?

Solution: Indoor air pollution refers to the contamination of indoor environments, mainly caused by cooking, heating, tobacco smoke, building materials, and cleaning products. Outdoor air pollution, on the other hand, occurs in the ambient environment and involves various pollutants from vehicles and industries.

Explain the concept of bioaccumulation in water pollution.

Solution: Bioaccumulation is the process by which certain pollutants, such as heavy metals or persistent organic pollutants, gradually accumulate within the tissues of aquatic organisms as they move up the food chain, leading to potential toxicity in higher trophic levels.

Discuss the impact of air pollution on climate change.

Solution: Air pollution, especially greenhouse gases like carbon dioxide and methane, contributes to climate change by trapping heat in the Earth's atmosphere, leading to global warming. This causes shifts in weather patterns, rising sea levels, and other climate-related phenomena.

How can we prevent water pollution caused by sewage disposal?

Solution: Proper sewage treatment facilities should be in place to remove harmful substances before discharge into water bodies. Promoting the use of septic tanks, constructing sewage treatment plants, and improving sanitation can help prevent water pollution from sewage disposal.

Discuss the role of environmental education in combating pollution.

Solution: Environmental education plays a significant role in raising awareness about pollution, its causes, and impacts. By educating individuals about sustainable practices and fostering a sense of responsibility towards the environment, we can encourage actions that lead to pollution prevention and reduction.

How can industrial pollution be controlled to minimize its impact on air and water?

Solution: Implementing cleaner production techniques, using pollution control devices, recycling and treating industrial waste, and adopting eco-friendly technologies can help minimize industrial pollution and reduce its negative impact on air and water.

Explain the role of rivers as a natural solution for filtering pollutants.

Solution: Rivers act as natural filters by carrying away pollutants through flowing water and sedimentation. The physical, chemical, and biological processes occurring in rivers help in purifying water and removing pollutants before it reaches the sea.

Describe the steps taken to address air pollution through international agreements.

Solution: International agreements like the Paris Agreement and the Montreal Protocol aim to address air pollution by reducing greenhouse gas emissions and phasing out ozone-depleting substances worldwide. These agreements promote global collaboration and emission reduction targets.

What role do non-governmental organizations (NGOs) play in pollution control?

Solution: NGOs play a vital role in raising awareness about pollution, advocating for stronger environmental legislation, and implementing pollution control programs. They work towards pollution prevention, conservation, and promoting sustainable practices.

Explain the concept of point source pollution in water bodies.

Solution: Point source pollution refers to the pollution that originates from a single identifiable source, such as a factory, sewage treatment plant, or oil spill, which directly discharges pollutants into water bodies, making it easier to trace and regulate.

Differentiate between primary and secondary air pollutants.

Solution: Primary air pollutants are released directly into the atmosphere from sources, such as vehicle emissions and industrial smokestacks. Secondary air pollutants are formed through chemical reactions between primary pollutants and other substances in the atmosphere.

How does noise pollution impact wildlife?

Solution: Noise pollution disrupts the natural habitats and behavior patterns of animals. It hampers their communication, disturbs their feeding and breeding cycles, and can lead to stress, disorientation, and reduced reproductive success.

Discuss the importance of monitoring air and water pollution levels.

Solution: Monitoring air and water pollution levels is crucial to assess the extent of pollution, identify sources, and determine the effectiveness of pollution control measures. It provides valuable data for policymakers and helps in formulating strategies to mitigate pollution.

What are the advantages of using alternative energy sources over conventional sources?

Solution: Alternative energy sources like solar, wind, and hydroelectric power offer several benefits. They produce minimal or no air pollution, reduce greenhouse gas emissions, are renewable, and contribute to sustainable development.

Explain how acid rain is formed and its consequences on the environment.

Solution: Acid rain is formed when sulfur dioxide and nitrogen oxides emitted by industries and vehicles react with atmospheric moisture, resulting in the formation of highly acidic compounds. Acid rain can damage forests, corrode buildings, and pollute water bodies, which can harm aquatic life.

What is the impact of water pollution on human livelihoods?

Solution: Water pollution affects various livelihoods that depend on clean water resources, such as fishing, agriculture, and tourism. Contaminated water can damage crops, kill fish, and reduce tourism revenue, disrupting local economies and people's livelihoods.

Discuss the role of individuals in preventing water pollution.

Solution: Individuals can prevent water pollution by minimizing the use of chemical-based household products, properly disposing of waste, conserving water, avoiding the dumping of hazardous substances into water bodies, and participating in community clean-up campaigns.

How does air pollution contribute to respiratory diseases like asthma?

Solution: Air pollution contains harmful substances like particulate matter, ozone, nitrogen oxides, and sulfur dioxide, which irritate the respiratory system. Prolonged exposure to polluted air can trigger or worsen respiratory conditions like asthma, leading to breathing difficulties and other health issues.

Explain how the improper disposal of electronic waste contributes to pollution.

Solution: Improper disposal of electronic waste releases toxic substances like lead, mercury, and cadmium into the environment. These pollutants leach into soil and water bodies, contaminating them and posing risks to human health and the ecosystem.