Solutions 15. AIR AROUND US - Exercise (NCERT Text Book) | Class 6 Science - Toppers Study

15. AIR AROUND US 

Exercise: 

Q1. What is the composition of air?

Ans: The air contains nitrogen 79%, oxygen 21%, carbon dioxide 1%, some other gass, water vapour. Air also contains dust particles and smoke.  

Q2. Which gas in the atmosphere is essential for respiration?

Ans: Oxygen is the gas, which is  essential for respiration.

Q3. How will you prove that air supports burning?

Ans: When we light a  candle in a tub with some filled water and also cover the candle with inverted glass. We observe that the candle blows out after burning for some time, and the water level inside the inverted glass rises up to some
extent. The air component, oxygen is used in burning, so remains space is occupied by water and it rises up. This shows that air support burning. 

Q4. How will you show that air is dissolved in water?

Ans: When water is boiled in a pan, we notice that some  bubbles form around the inner surface of the pan. It means air is dissolving in water. 

Q5. Why does a lump of cotton wool shrink in water?

Ans: A lump of cotton wool shrinks when immersed in water. This is because air present in the cotton wool escapes. Thus, the volume of the cotton wool decreases.

Q6. The layer of air around the earth is known as ___________.

Ans: The layer of air around the earth is known as atmosphere.

Q7. The component of air used by green plants to make their food, is ______.

Ans: The component of air used by green plants to make their food, is carbon dioxide.

Q8. List five activities that are possible due to the presence of air.

Ans: 

(i) Respiration

(ii) Burning

(iii) Photosynthesis

(vi) Flying of kites

(v) Movement of sailing yachts, gliders, parachutes, airplanes

(vi) Generation of electricity by windmills

Q9. How do plants and animals help each other in the exchange of gases in the atmosphere?

Ans: All animals do respiration and they release carbon dioxide in the atmosphere and take oxygen during this process whereas, plants utilise carbon dioxide in the process of photosynthesis and release oxygen. Here we see that gaseous exchanges take place among animals and plants.