A lump of cotton wool has a lot of air trapped inside the space present in its fibers. When this lump of cotton is immersed in water, all the air is replaced by water. Because of this, the cotton lump shrinks in water.
You will often see long chimneys in factories why do you think so it is present? Check your Answers
Chimneys take harmful gases and smoke of the factories away and prevent it from entering our nose.
Why no water enters the bottle when it is inverted into a bucket of water vertically? Check your Answers
When an empty glass bottle is inverted into a bottle of water vertically, water does not enter the bottle because the bottle contains air. The bottle is already filled with air and hence water does not enter inside it.
The organism is earthworm.
They respire by taking oxygen present in the soil. Also make deep burrows and holes in the soil through which the air reaches them for respiration.
i. What phenomena is shown in the picture?
ii. why do you think the candle in the second image stops burning? Check your Answers
i. oxygen is necessary for burning.
ii. when the burning candle is covered with a gas jar then the fresh supply of air to the candle is cut off and hence it stops burning.
i. What is this above picture depicting?
ii. How does air help in the above process shown? Check your Answers
i. A windmill being used to run a pump to draw water from the ground.
ii. Air rotates the wind mill blades continuously. When the blades rotate the crank attached to the blades also rotate. When the crank rotates then its U-bend lifts pump rod up and down continuously. The rod works the pump which lifts the water from ground.
List the sources of dust particles that come into air.
Why is it said that always breathe through nose and not through our mouth?
Air is a matter and is attracted towards earth due to gravity. Because of this reason air density is more at earth's surface but decreases as we go up and hence air becomes thinner as we go at higher altitudes.
Carbon dioxide leads to global warming. It is important to have carbon dioxide in air. Why do you think so? Check your Answers
Carbon dioxide is an important raw material for photosynthesis by which the plant makes food.
What would happen if the percentage of oxygen and nitrogen in the atmosphere was reversed? Check your Answers
If the percentage of oxygen in the air reaches to around 78% then, if any substance catches fire it will become difficult to extinguish the fire, because oxygen supports combustion.
The plants leave carbon dioxide at night. On the basis of this it is that in the night if you sleep under the tree, you will not get oxygen, but get carbon dioxide which can be suffocating.
The gas X is colourless and odourless having a slightly sour taste which is a minor component of air. It is moderately soluble in water. This gas neither burns nor support burning. It rather extinguishes a burning fire. If there were no gas X in air, there would be no animals or plants on earth.