2. What are the three main components of Earth's surface?

The atmosphere is the blanket of air surrounding Earth, the lithosphere is the outer crust of the planet, and the hydrosphere is the water covering 75% of the Earth's surface, including seas, oceans, rivers, lakes, and ponds.

5. How does the atmosphere control climate?

The atmosphere keeps the average temperature of the Earth fairly stable during the day and during the year. It prevents a sudden increase in temperature during the day and slows down the escape of heat during the night.

7. How is rain formed?

When water bodies are heated during the day, a large amount of water evaporates and goes into the air. The hot air rises up carrying the water vapours with it. As the air rises, it expands and cools. The cooling causes the water vapour in the air to condense in the form of tiny droplets, and when the drops have grown big and heavy, they fall down in the form of rain.

8. What causes air pollution?

The burning of fossil fuel causes air pollution as it produces oxides of nitrogen and sulphur, which dissolve in rainwater to cause acid rain, and suspended particles, in the form of unburnt carbon particles or hydrocarbons, which decrease visibility and cause smog.

11. What is the impact of releasing water from dams on aquatic life?

Releasing water from dams can affect the temperature of water bodies, which can encourage the growth of some life forms while damaging others, thereby affecting the balance between various organisms.

15. How can soil erosion be prevented?

Soil erosion can be prevented by planting vegetation, such as trees and crops, which bind the soil particles together and prevent soil from being washed away. Avoiding mass-scale deforestation is also essential in preventing soil erosion.

16. What is the water cycle? Explain the significance of underground water.

The water cycle involves the process in which water evaporates and falls on the land as rain, then flows back into the sea via rivers. Underground water is significant as it seeps into the soil, becomes part of the freshwater reservoir, and supplies water to terrestrial animals and plants.

17. What is the nitrogen cycle? Explain the role of nitrogen-fixing bacteria.

The nitrogen cycle is when atmospheric nitrogen enters soil and water as simple forms, and then living beings convert it into complex molecules and release it back as simple nitrogen molecules. Nitrogen-fixing bacteria convert atmospheric nitrogen into essential nutrients for all life forms, such as nitrates and nitrites.

18. How is carbon cycled in the biosphere? Explain the role of photosynthesis and respiration.

Carbon is cycled via photosynthesis, where CO₂ is converted to glucose. Respiration oxidizes glucose back to CO₂, returning it to the atmosphere. Fossil fuel combustion adds CO₂ too. Photosynthesis and respiration balance CO₂ levels. Carbon is stored in biomass, soil, and oceans.

19. What is the greenhouse effect and how does it work?

The greenhouse effect is the process by which certain gases, like carbon dioxide, trap heat radiations, leading to a rise in the average temperature of the planet. This phenomenon relates to global warming and its impact on the environment.

20. What is the relationship between the greenhouse effect and global warming?

The greenhouse effect is directly linked to global warming as it is caused by the buildup of greenhouse gases, including carbon dioxide, in the atmosphere. This results in an increase in the temperature of the planet and has a significant impact on the environment.