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Q1. The layer of air that surrounds the Earth is called the:
The atmosphere is the thick blanket of air that surrounds the Earth. It protects us from harmful rays and gives us air to breathe.
Q2. The two main gases present in the air are:
Air is mainly made up of nitrogen (about 78%) and oxygen (about 21%). Other gases like carbon dioxide and argon are present in small amounts.
Q3. The percentage of oxygen in the air is about:
Oxygen makes up about 21% of the air. It is the gas that all living things need to breathe and survive.
Q4. The percentage of nitrogen in the air is about:
Nitrogen is the most abundant gas in the air, making up about 78%. It helps plants grow and is used to make fertilizers.
Q5. Carbon dioxide is present in the air in very small amounts, about:
Carbon dioxide is only about 0.03% of the air. Even this small amount is important for plants to make food through photosynthesis.
Q6. Air is needed for:
Air is essential for all living things to breathe. It is also needed for burning and for things like inflating tyres.
Q7. Air helps in burning because it contains:
Oxygen in the air supports burning. Without oxygen, a fire cannot burn.
Q8. Air is used to inflate things like:
Air is pumped into tyres and balloons to fill them up. This is called inflating.
Q9. Air has:
Air has weight even though we cannot see it. This is why the atmosphere presses down on us.
Q10. Air exerts:
Air exerts pressure in all directions because it has weight. This pressure is called atmospheric pressure.
Q11. When we sip juice through a straw, we use:
When we suck air from the straw, the air pressure outside pushes the juice up into the straw. This is how we drink through a straw.
Q12. Ink rises in a fountain pen due to:
When we press the ink filler, air is pushed out. When we release it, air pressure pushes the ink up into the pen.
Q13. A syringe works because of:
When the plunger of a syringe is pulled back, air pressure pushes the liquid or medicine into the syringe. This is how injections are filled.
Q14. The balance between carbon dioxide and oxygen in the air is maintained by:
Animals breathe in oxygen and breathe out carbon dioxide. Plants take in carbon dioxide and release oxygen, keeping the balance.
Q15. Which gas is released by plants during photosynthesis?
Plants take in carbon dioxide and water to make food. During this process, they release oxygen into the air.
Q16. Which gas is released by animals during breathing?
Animals breathe in oxygen and breathe out carbon dioxide. This carbon dioxide is used by plants for photosynthesis.
Q17. Air pollution is caused by:
Harmful gases and smoke from factories, vehicles and burning waste pollute the air. This makes the air dirty and unhealthy.
Q18. One way to reduce air pollution is by:
Trees absorb harmful gases and give out clean oxygen. Planting more trees helps in keeping the air clean.
Q19. The substance that dissolves in a liquid is called the:
The solute is the substance that gets dissolved. For example, salt is the solute when it dissolves in water.
Q20. The liquid in which a substance dissolves is called the:
The solvent is the liquid that dissolves the solute. Water is called a universal solvent because it dissolves many things.
Q21. The mixture formed when a solute dissolves in a solvent is called a:
When salt dissolves in water, it forms a salt solution. A solution is the uniform mixture of solute and solvent.
Q22. In a salt solution, salt is the:
In salt solution, salt is the substance that dissolves in water. So, salt is the solute.
Q23. In a salt solution, water is the:
In salt solution, water is the liquid that dissolves the salt. So, water is the solvent.
Q24. The process by which a liquid changes into vapour on heating is called:
Evaporation is when a liquid turns into vapour or gas. Water evaporates when heated and turns into steam.
Q25. Evaporation is used to:
When a salt solution is heated, water evaporates and salt is left behind. This is how salt is obtained from sea water.
Q26. Distillation is the process of:
Distillation involves boiling a liquid and then cooling the vapour to get pure liquid. It is used to purify water.
Q27. The process of settling down of heavy impurities in water is called:
When muddy water is kept still, heavy mud particles settle at the bottom. This settling is called sedimentation.
Q28. The process of pouring out clear water without disturbing the settled impurities is called:
After sedimentation, the clean water on top is gently poured into another container. This method is called decantation.
Q29. The process of passing water through a filter paper to remove insoluble impurities is called:
Filtration uses a filter paper or cloth that traps solid impurities. Clean water passes through, leaving dirt behind.
Q30. Impurities that do not dissolve in water are called:
Insoluble impurities like sand and mud do not dissolve in water. They can be removed by filtration or sedimentation.
Q31. Impurities that dissolve in water are called:
Soluble impurities like salt and sugar dissolve in water. They cannot be removed by filtration but can be removed by distillation.
Q32. Potable water means:
Potable water is clean and safe for drinking. It does not contain harmful germs or impurities.
Q33. Water can be purified by boiling for:
Boiling water for 20 minutes kills all the germs and bacteria. This makes the water safe to drink.
Q34. Chlorine gas is used to:
Chlorine is a chemical that kills harmful germs in water. It is added to drinking water to make it safe.
Q35. Water is called the universal solvent because:
Water can dissolve more substances than any other liquid. This is why it is called the universal solvent.
Q36. The process of separating a liquid from a solution by boiling and cooling is called:
Distillation involves boiling the solution to make vapour and then cooling it to get pure liquid. This purifies water.
Q37. Air pressure helps in:
Air pressure is used in many daily activities. We use it to drink juice, fill ink in pens and use syringes.
Q38. When we boil water for 20 minutes, we:
Boiling water for 20 minutes kills all disease-causing germs. This is the easiest way to purify water at home.
Q39. The nitrogen in the air is used by plants with the help of:
Special bacteria in the soil convert nitrogen into a form that plants can use. This helps plants grow.
Q40. The main cause of air pollution is:
Burning coal, petrol and diesel releases harmful gases and smoke. This is the main cause of air pollution.
Q41. A filter paper is used in the process of:
In filtration, water passes through a filter paper that traps dirt and impurities. Clean water comes out on the other side.
Q42. The process of decantation is used after:
After the heavy impurities settle down, the clean water is poured out. This pouring out is called decantation.
Q43. A mixture of sugar and water is a:
Sugar dissolves completely in water to form a clear mixture. This is called a sugar solution.
Q44. Which gas is the most abundant in the atmosphere?
Nitrogen makes up about 78% of the air. It is the most abundant gas in the atmosphere.
Q45. The process of evaporation is used to:
Sea water is heated so that water evaporates. The salt that is left behind is collected.
Q46. Air pressure is created because:
The weight of air pressing down on us creates air pressure. This pressure is felt all around us.
Q47. A fountain pen works on the principle of:
When the ink filler is pressed, air is removed. Air pressure then pushes the ink into the pen.
Q48. The water that is safe for drinking is called:
Potable water is clean and free from germs. It is safe for drinking and cooking.
Q49. Air is a mixture of gases because it contains:
Air contains many gases like nitrogen, oxygen, carbon dioxide and argon. This makes it a mixture.
Q50. The balance of gases in the air is disturbed by:
Cutting down trees reduces oxygen production. Pollution adds harmful gases, disturbing the natural balance of air.
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Q51. When a liquid is heated and the vapour is cooled to get pure liquid, the process is called:
Distillation purifies liquids by boiling and then condensing the vapour. It is used to get pure water from salty water.
Q52. Mud in water is an example of:
Mud does not dissolve in water and settles down. It is an insoluble impurity that can be removed by filtration.
Q53. A straw works because of:
When we suck air from the straw, the air pressure outside pushes the juice into the straw. This brings the juice to our mouth.
Q54. We can reduce air pollution by:
Using buses, trains and cycles reduces the number of vehicles on the road. This lowers the smoke and pollution in the air.
Q55. Salt can be separated from salt water by:
When salt water is heated, water evaporates and salt is left behind. This is how salt is obtained.
Q56. The process of sedimentation helps in:
Sedimentation allows heavy insoluble impurities like sand to settle at the bottom. The clean water can then be poured off.
Q57. Chlorine is added to water to:
Chlorine is a disinfectant that kills harmful germs. It is used in water treatment plants to make water safe to drink.
Q58. A doctor uses a syringe because of:
When the plunger is pulled, air pressure pushes the medicine into the syringe. This allows the doctor to give injections.
Q59. The oxygen in the air is used by:
All living things, including animals and plants, need oxygen to breathe. Plants also need oxygen at night.
Q60. Boiling water for 20 minutes is a method of:
Boiling water kills germs and bacteria that cause diseases. This makes the water safe for drinking.