Class 7, NCERT (CBSE) Social Science (Geography)
Our Environment - Air
Solutions of Sample Questions
Answer Q.1: When air in any place become hotter than its surroundings then it expands, becomes lighter and begins to move upwards. Cold air from the surrounding area immediately rushes to fill in the gap. This is a continuous process since temperature is always changing. That is how air-circulation takes place.
Answer Q.2: Air pressure is the pressure exerted by the weight of air. As we go up the layers of atmosphere, the pressure falls rapidly. The air pressure is the highest at sea level. It decreases with increase in height.
Horizontally the distribution of air pressure is influenced by the temperature of air at a given place. In areas where temperature is high the air gets heated and rises. This creates a low-pressure area. Low pressure is associated with cloudy skies and wet weather. In areas where temperature is low, the air is cold and heavy. Heavy air sinks and creates a high pressure area.
Answer Q.3: Horizontally moving air from high pressure area to low pressure area is called Wind. Fast blowing wind is called Storm. Slow or gently blowing wind is called Breeze.