1.When water in a beaker gets heated air bubbles can be seen coming out of the water. Why does this happen?

The air dissolved in water comes out as bubbles when it is heated.

2. Why do fish dies when it is taken out of water?

Fishes respire oxygen dissolved in the water. So when it is taken out of water it cannot respire and dies.

3. What is meant by wind?

Wind is the flow of atmospheric air.

4. Define atmosphere.

The layer of air covering the Earth is called atmosphere.

5. What are the benefits of air being present in soil?

• Microorganisms get air.
• It helps the soil to absorb water.

6. What are the advantages of having air in water?

Aquatic plants and organisms use the air present in water.

7. Air has no colour. It is its characteristic. Similarly write down some other characteristics you know.

• Air has no smell.
• Air has no definite shape.
• Air occupies space.
• Air has weight.

8. Ravi inverted a glass tumbler into water in a flat vessel. Water did not enter the glass. But when he tilted the glass to one side air bubbles came out and water entered the glass. What is the reason for this? What did he understand from this?

When he inverted the glass straight into water it was full of air and hence water did not enter the glass. When he tilted the glass, the air in the glass went out as bubbles and water entered the glass. From this he understood that air occupies space.

9. Giving  a piece of chalk into your hand the teacher asked, " How will you test whether there is any air in it". What will you do?

Put the chalk into a vessel containing water. Air trapped between the molecules of chalk comes out as bubbles. This proves that air is present in chalk.

10. "Fish released into boiled and cooled water dies." Do you agree with this statement?

Yes. When water is boiled the oxygen dissolved in it goes out. Fish uses the dissolved oxygen present in water. Since this water is devoid of air the fish dies.

11. Why do coconut leaf tops and paper tops rotate in wind?

Because of the force of wind the tops rotate.

12. "Dry soil contains air". Is this statement correct? Give your opinion.

The statement is correct. If you put some dry soil in a glass of water you can see air bubbles coming out of the soil. This proves the statement.