What is around Us? — Important Questions

Nitrogen

Step 1: The Atmosphere is a mixture of several gases. Step 2: The chapter states the Atmosphere contains approximately 78% Nitrogen, 21% Oxygen, and 1% other gases. Step 3: Therefore, Nitrogen is the most abundant gas in the Atmosphere. Step 4: Oxygen comes second at 21%, which is crucial for breathing but is NOT the most abundant gas. Step 5: Carbon dioxide and Ozone are present in very small amounts — Ozone is especially important for absorbing ultraviolet rays, but is not the most abundant gas.

It absorbs ultraviolet rays from the Sun and protects the Earth

Step 1: The Sun emits harmful ultraviolet (UV) rays along with light and heat. Step 2: Ozone gas is present in the upper layers of the Atmosphere and forms a protective shield. Step 3: Ozone absorbs these ultraviolet rays, preventing them from reaching the Earth's surface in harmful amounts. Step 4: Without Ozone, UV rays could cause serious health problems like skin diseases and eye damage. Step 5: Cloud formation is related to water vapour and condensation, not Ozone — so Option A is incorrect.

Biosphere

Step 1: The chapter explains that after the formation of the Earth's solid, liquid, and gas layers, life developed. Step 2: The Biosphere is the sphere that includes all living organisms — plants, animals, insects, and human beings. Step 3: It exists where parts of the Lithosphere, Hydrosphere, and Atmosphere overlap to support life. Step 4: The other three spheres (Lithosphere, Hydrosphere, Atmosphere) form the non-living environment that supports the Biosphere. Step 5: Earth is unique in the solar system because it is the only planet with a Biosphere.

Condensation

Step 1: Due to heat, water from oceans, lakes, and rivers turns into water vapour — this process is called Evaporation. Step 2: This water vapour rises into the atmosphere and mixes with air as moisture. Step 3: When this vapour cools down, it turns back into liquid water — this process is called Condensation. Step 4: Condensation leads to the formation of dew, fog, clouds, and precipitation (rain, snow). Step 5: Precipitation is the result of condensation (water falling as rain or snow), not the process itself — so it is incorrect here.