Important Questions: Air - Class 7 MCQ

Hydrocarbon fuels like methane (CH₄) burn in the presence of oxygen to produce carbon dioxide and water. This process of combustion releases energy. 

The air around us acts like a cozy blanket, protecting us from the strong rays of the sun. Without this protective layer, we would either feel too hot during the day or too cold at night. This blanket of air helps to keep the Earth at just the right temperature for us to live comfortably.

Nitrogen is the most plentiful gas in the air. When we inhale, we take some amount of nitrogen into our lungs and exhale it. Plants cannot take nitrogen directly from the air. Bacteria in the soil help plants use nitrogen.

Wind is the movement of air from high pressure areas to low pressure areas. You can feel wind blowing gently on a calm day or strongly during a storm. Wind helps in spreading seeds, carrying pollen, and even powering wind turbines to create electricity.

Celsius is the standard unit we use to measure how hot or cold something is. Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius. 

• True! The temperature decreases as we move from the equator towards the poles. This happens because the amount of solar energy, called insolation, decreases from the equator towards the poles.
• That's why places near the poles are colder compared to places near the equator where it's warmer.

The water vapor in the air is called humidity. This is how we describe how much water is in the air around us.

Astronauts wear special protective space suits because the lack of air pressure in space means there is no external force to counteract the pressure exerted by their bodies. Without these suits, the internal pressure would cause their blood vessels to burst, leading to severe injury or death. The suits also provide protection against extreme temperatures, micrometeoroids, and offer a supply of oxygen for breathing.