Ans. Mountaineers carry oxygen cylinders with them, while climbing high mountains because as we go up higher and higher, level of oxygen decreases.
Ans. Burning of some material releases smoke and soot which is harmful, thus we feel suffocated in a closed space, where some material is burning.
Ans. Air contains water vapors and dust particles which stick to transparent glass of windows. Thus glass of windows appears hazy.
Ans. It is not advisable to breathe through our mouth because if we do that, harmful dust particles may enter our body.
Ans. No, water will not move inside the bottle because it was filled completely with air and there was no space for air to escape.
Ans. When the bottle was tilted, the air was able to come out in the form of bubbles, and water filled up the empty space that the air has occupied.
Ans. Carbon dioxide enters the atmosphere in the following way:
i. Respiration by plants and animals
ii. Burning of fuel
Ans. Two uses of wind energy
i. It is used to pump the ground water.
ii. It is used to generate electricity with the help of windmills.
Ans. It shows the direction in which the air is moving at that place. Thus, if the wind is blowing from the north, the arrow will point towards the northern direction.
Ans. No, it is not possible to light up a candle on the moon because there is no oxygen on the moon. Oxygen is one of the basic requirements for burning.
Ans. When it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation, animals living in the soil such as earthworms have to come out for respiration.
Ans. The amount of oxygen component inside the glass is limited. When most of this oxygen is used up by the burning candle, it can no longer burn and blows out.
Ans. When air comes in contact with a cool surface, air gets cooled and it can no longer hold as much water vapor. Thus water vapor in the air condenses and drops of water appear on cool surface.
Ans. The burning of fuel produces smoke. Smoke contains a few gases and fine dust particles and is often harmful. Long chimneys in factories take the harmful smoke and gases away from us.
Ans. We inhale air when we breathe through our nostrils. Fine hair and mucus are present inside the nose to prevent dust particles from getting into the respiratory system.
Ans. Policemen regulating traffic at a crowded crossing wear a mask to cover his face to protect himself from the polluted air that emits from the vehicles which may enters his nose and cause him serious problem.
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