Air

Q25. What is wind?

Ans. The movement of air from high pressure area to low pressure areas is called wind.

Q26. Why do we feel uncomfortable on a humid day?

Ans. Sweat from our body does not evaporate easily, making us feel very uncomfortable.

Q27. What do you understand by climate of a place?

Ans. The average weather condition of a place for a longer period of time represents the climate of a place.

Q28. In which layers of the earth's atmosphere does the temperature rises very rapidly with increasing height?

Ans. In thermosphere temperature rises very rapidly with increasing height.

Q29. What causes flooding of low lying areas?

Ans. When trees on hill sides are cut, rainwater flows down the bare mountains and can cause flooding of low lying areas.

Q30. How are winds named?

Ans. A wind is named after the direction from which it blows, e.g. the wind blowing from the west is called westerly.

Q31. Which two gases make the bulk of the atmosphere?

Ans. Nitrogen and oxygen are two gases which make up the bulk of the atmosphere.

Q32. Which gas creates greenhouse effect in the atmosphere?

Ans. Carbon dioxide released in the atmosphere creates a greenhouse effect in the atmosphere.

Q33. Name three types of rainfall.

Ans. On the basis of mechanism, there are three types of rainfall: the convectional rainfall, the orographic rainfall and the cyclonic rainfall.

Q34. What is air pressure?

Ans. Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface.

Q35. What are the three main types of winds?

Ans. Winds can be broadly divided into three types: Permanent winds, Seasonal winds and Local winds.

Q36. How does carbon dioxide create greenhouse effect?

Ans. Carbon dioxide released in the atmosphere creates a greenhouse effect by trapping the heat radiated from the earth.

Q37. Why does hot air rise & cold air sink?

Ans. When air is heated, it expands, becomes lighter and goes up. Cold air is denser and heavy. That is why it tends to sink down.

Q38. Why wet clothes take longer time to dry on a humid day?

Ans. Wet clothes take longer time to dry on a humid day because the air has a plenty of water vapor already present in it and is not able to accommodate more water vapor.

Q39. What is global warming?

Ans. When the level of carbon dioxide increases in the atmosphere due to factory smoke or car fumes, the heat retained increases the temperature of the earth. This is called global warming.

Q40. Why poles are covered with snow?

Ans. The amount of insolation decreases from the equator towards the poles. Therefore, the temperature decreases in the same manner. That’s why poles are covered with snow.

Q41. Why rain is important for us? How plants can help with water conservation?

Ans. Most of the ground water comes from rainwater. Plants help preserve water. When trees on hill sides are cut, rainwater flows down the bare mountains and can cause flooding of low lying areas.

Q42. How do bacteria help plants use nitrogen?

Ans. Plants need nitrogen for their survival. They cannot take nitrogen directly from the air. Bacteria that live in the soil and roots of some plants take nitrogen from the air and change its form so that plants can use it.