NCERT Class 6th Science Chapter 11 Air Around Us Question Answers

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NCERT Class 6th Science Chapter 11 Air Around Us Question Answers

1. What is the composition of air?

Air is a mixture of several gases and components. The major components of air are:

  • Nitrogen: Makes up about 78% of the air.
  • Oxygen: Comprises around 21% of the air.
  • Carbon Dioxide: Present in small quantities, about 0.03% to 0.04%.
  • Water Vapour: Varies depending on location and weather conditions.
  • Other Gases: Includes argon, helium, neon, and others, which together make up less than 1%.
  • Dust and Smoke: Fine particles of dust and smoke are also present in the air, especially in polluted areas.

2. Which gas in the atmosphere is essential for respiration?

Oxygen is the gas in the atmosphere that is essential for respiration. All living organisms, including humans and animals, require oxygen to breathe and to carry out cellular respiration, a process that releases energy from food.

3. How will you prove that air supports burning?

To prove that air supports burning, you can perform the following simple experiment:

  • Materials Needed: Two small candles, a glass tumbler, and matches.
  • Steps:
    1. Fix two candles of the same size on a table.
    2. Light both the candles.
    3. Cover one of the candles with an inverted glass tumbler, while leaving the other uncovered.
    4. Observe what happens to both candles.
  • Observation: The candle that is covered by the glass tumbler will extinguish after a short while, while the other candle continues to burn.
  • Conclusion: The candle inside the tumbler extinguishes because it uses up the limited oxygen available within the glass. The other candle continues to burn because it has an ample supply of oxygen from the surrounding air. This proves that air (specifically oxygen in the air) supports burning.

4. How will you show that air is dissolved in water?

You can demonstrate that air is dissolved in water through the following activity:

  • Materials Needed: A glass or metal container, water, and a heat source.
  • Steps:
    1. Fill a container with water.
    2. Heat the water slowly, but do not bring it to a boil.
    3. Observe the inner surface of the container carefully as it heats up.
  • Observation: As the water is heated, tiny bubbles will form on the inner surface of the container before the water begins to boil.
  • Conclusion: The bubbles are formed by the air that was dissolved in the water. When the water is heated, the dissolved air escapes from the water, proving that air is indeed dissolved in water.

5. Why does a lump of cotton wool shrink in water?

A lump of cotton wool shrinks in water because water fills the air spaces between the cotton fibers. The cotton fibers are held apart by the trapped air in the wool. When the cotton wool is submerged in water, the air is displaced by water, causing the fibers to come closer together, and as a result, the cotton wool shrinks.

6. The layer of air around the earth is known as ___________.

The layer of air around the Earth is known as the atmosphere. The atmosphere is a thin layer of gases that surrounds the planet and extends up to many kilometers above the Earth's surface.

7. The component of air used by green plants to make their food, is ___________.

The component of air used by green plants to make their food is carbon dioxide. During the process of photosynthesis, plants absorb carbon dioxide from the air and use it, along with sunlight and water, to produce food (glucose) and oxygen.

8. List five activities that are possible due to the presence of air.

Five activities that are possible due to the presence of air include:

  1. Breathing (Respiration): All living organisms, including humans, animals, and plants, need air (specifically oxygen) to breathe and survive.
  2. Burning: Combustion or burning of fuels such as wood, coal, and natural gas is possible because of the presence of oxygen in the air.
  3. Winnowing: The process of winnowing, which separates grains from chaff, relies on the movement of air.
  4. Flying Kites and Parachutes: The movement of air (wind) allows activities like flying kites, gliders, and parachutes.
  5. Generating Wind Energy: Windmills use the movement of air to generate electricity by converting wind energy into mechanical energy.

9. How do plants and animals help each other in the exchange of gases in the atmosphere?

Plants and animals help each other in the exchange of gases in the atmosphere through the processes of respiration and photosynthesis:

  • Animals: During respiration, animals inhale oxygen from the air and exhale carbon dioxide as a waste product.
  • Plants: Plants absorb the carbon dioxide released by animals and use it in the process of photosynthesis to make their food. During photosynthesis, plants release oxygen as a byproduct, which is then used by animals for respiration.

This interdependence helps maintain the balance of oxygen and carbon dioxide in the atmosphere, supporting life on Earth.

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