NCERT Class VI Science Solutions: Chapter 15 – Air Around us Part 4

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LONG ANSWER QUESTIONS

Question 17:

Explain the following observations very briefly

  1. A firki does not rotate in a closed area.

  2. The arrow of weather cock points towards a particular direction at a particular moment.

  3. An empty glass in fact is not empty.

  4. Breathing through mouth may harm you.

Answer:

  1. Motion of firki is based on the pressure/force applied by air on the firk. A firki does not rotate in a closed area because of lack of air movement.

  2. The arrow of weather cock points towards a particular direction as it shows the direction in which the air is moving at that place at a particular moment.

  3. An empty glass in fact is not empty. It is filled with air. Air is present everywhere.

  4. Breathing through mouth may harm us because we may inhale dust if present in air which may enter our respiratory system and damage out health.

Question 18:

Write just a few sentences for an imaginary situation if any of the following gases disappear from the atmosphere

  1. Oxygen

  2. Nitrogen

  3. Carbon dioxide

Answer:

  1. There will be no life on the earth. Oxygen is vital for life. It helps in burning, respiration, photosynthesis etc. Oxygen is basic need of all living beigns.

  2. Nitrogen does not support burning. If nitrogen gas disappear from the atmosphere, thing will burn very fast.

  3. Carbon dioxide is needed for photosynthesis which occurs in green plants. In its absence, plants will not be able to prepare their food and hence, without carbon dioxide there would be no plants or animals on the earth.

    Image of Photosynthesis

    Image of Photosynthesis

    Image of Photosynthesis

Question 19:

Paheli kept some water in a beaker for heating. She observed that tiny bubbles appeared before the water started to boil. She boiled the water for about 5 minutes and filled it in a bottle up to the brim and kept the bottle air tight till it cooled down to room temperature.

  1. Why did the tiny bubbles appeared?

  2. Do you think tiny bubbles will appear on heating the water taken out from the bottle? Justify your answer.

Answer:

  1. Air is dissolved in water in the form of oxygen. Tiny bubbles are formed, when air present in the water escape on boiling it.

    So, tiny bubbles appeared due to the evolution of air dissolved in water.

  2. No, tiny bubbles will not appear as there is no dissolved air in this water.

Question 20:

On a Sunday morning Paheli’s friend visited her home. She wanted to see some flowering plants in the nearby garden. Both of them went to the garden. While returning from the garden they also observed some flowering plants on the road side. Hut to their surprise they found that the leaves and flowers of these roadside plants were comparatively very dull. Can you help them to know why?

Answer:

The road side plants had probably some dust and soot deposited on them and thus appeared dull.

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