Air Class 7 Worksheet Geography Chapter 4

Q.1. What is the instrument that measures the amount of rainfall?

Rain Gauge

Q.2. What do you understand by climate of a place?

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

Q.3. Why amount of insolation decreases from equator towards poles?

Sun rays falls almost vertically on the equator and covers less space whereas sun rays falls at slanting angle on the poles and covers more space. Thus, the amount of insolation decreases from the equator towards the poles.

Q.4. How does nature maintain a balance of oxygen and carbon dioxide in the atmosphere? What is the result of this balance get disturbed?

Oxygen is the second most plentiful gas in the air. Humans and animals take oxygen from the air as they breathe. Green plants produce oxygen during photosynthesis. In this way oxygen content in the air remains constant. If we cut trees then this balance gets disturbed. Carbon dioxide is another important gas. Green plants use carbon dioxide to make their food and release oxygen. Humans or animals release carbon dioxide. The amount of carbon dioxide released by humans or animals seems to be equal to the amount used by the plants which make a perfect balance. However, the balance is upset by burning of fuels, such as coal and oil. They add billions of tons of carbon dioxide into the atmosphere each year. As a result, the increased volume of carbon dioxide is affecting the earth’s weather and climate.

Q.5. What is the standard unit of measurement for temperature?

The standard unit of measuring temperature is degree Celsius.

Q.6. How are winds named?

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

Q.7. Why do astronauts wear space suits on the moon?

Astronauts have to wear special protective space suits filled with air when they go to the moon. If they did not wear these space suits, the counter pressure exerted by the body of the astronauts would make the blood vessels burst. The astronauts would bleed.

Q.8. Write a short note on the distribution of air pressure in atmosphere?

Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface. As we go up the layers of atmosphere, the pressure falls rapidly. The air pressure is highest at sea level and decreases with height. Horizontally the distribution of air pressure is influenced by 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.

Q.9. Which gas protects us from harmful sun rays?

Ozone protects us from the harmful effect of the sun rays.

Q.10. What are the three main types of winds?

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

Q.11. Why is the atmosphere essential for life?

All living beings on this earth depend on the atmosphere for their survival. It provides us the air we breathe and protects us from the harmful effects of the sun’s rays. Without this blanket of protection, we would be baked alive by the heat of the sun during day and get frozen during night. So it is this mass of air that has made the temperature on the earth liveable.

Q.12. What is the composition of the atmosphere?

The air we take in while breathing is actually a mixture of many gases. Nitrogen (78%) and oxygen (21%) are two gases which make up the bulk of the atmosphere. Carbon dioxide (O.3%), helium, ozone, argon (0.93%) and hydrogen are found in lesser quantities. Apart from these gases, tiny dust particles are also present in the air. The pie chart gives you the percentage of different constituents of air.

Q.13. What is the role of the ozone layer?

Ozone layer protects us from the harmful effect of the sun rays.

Q.14. What is global warming?

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.

Q.15. How do bacteria help plants use nitrogen?

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.