Air and water

Answer the following questions:

1. What is the percentage of oxygen in the atmosphere?

Ans: The percentage of oxygen in the atmosphere is 21%  .

2. Name the instrument which is used to measure atmosphere pressure.

Ans: The instrument which is used to measure atmosphere pressure is Barometer .

3. Name two methods of purify water.

Ans : Boiling and filtration are two methods of purify water .

4. What is loading

Ans: Loading is process in which heavy particles settle down at the bottom .

5. Write an activity to show that air occupies space.

Ans: • Take an empty glass and a bucket half filled with water.

• Put the inverted glass into the bucket of water. This must be done very quickly and forcefully. The glass must be kept straight and put inside in an inverted position.

• The water does not enter the inverted glass. Why? The air present in the empty glass prevents the water from entering it.

• When we tilt the glass held in water, we find that of air present in the glass goes out in the form of air bubbles. As the air from the glass escapes, water starts entering the glass. This shows that the glass which appears to be empty to us actually filled with air. So, it proves that air occupies space.

6. Explain the filtration with the help of a diagram.

Ans: To filter a mixture of water and sand, we make a cone of filter paper and keep it inside a funnel. The mixture is poured into the funnel. The sand does not pass through the filter paper and remains behind on the filter paper. This is called reduce.

The clear water comes out of the filter paper and is collected in the flask below the funnel. This is called filtrate. This method of purifying water is called filtration .