Why does a lump of cotton wool shrink in water?

3

(a)

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

3

(a)

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

3

(a)

Garima observed that when she left her tightly capped bottle full of water in the open sunlight, tiny bubbles were formed all around inside the bottle. Help Garima to know why it so happened?

3

(a)

Nitrogen in air is important for living organisms. Specify.

3

(a)

The gas Y is colourless and odourless having a slightly sour taste and is a minor component of air. It is moderately soluble in water. This gas neither burns nor supports burning. It rather extinguishes a burning fire. If there were no gas Y in air, there would be no animals or plants on the earth.
(a) Identify gas Y.
(b) In what percentage, gas Y is present in air?
(c) State two ways in which gas Y is added to the air.
(d) Gas Y is necessary for the existence of life. Why?

3

(a)

During any fire incident, it is advised to
(a) wrap a towel or woollen blanket over the burning object.
(b) use a fire extinguisher to stop the fire.
Why are these methods advised? Give reasons.

3

(a)

Air takes the shape, smell, etc from the object/ place it is present in. Explain.

3

(a)

Observe the figure given below depicting distribution of some components present in air and answer the following questions:

(a) Identify all the components.
(b) What purpose is served by component (iii)?
(c) Do the values or percentages of these components vary?

3

(a)

A transparent glass window appears hazy when not wiped off regularly. Can you suggest a reason?

3

(a)

Explain why air is considered a mixture.

3

(a)

Is winnowing possible in a closed room? Give. reason

3

(a)

How can you say that both animals and plants are dependent on each other for their survival?

3

(a)

What is windmill? Write two uses of windmill.

3

(a)

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

3

(a)