8.2: Earth and its Atmosphere

Earth's atmosphere composition

Approximately 78% nitrogen, 21% oxygen, and small amounts of other gases like carbon dioxide, water vapour, and noble gases.

Early atmosphere composition

Mostly carbon dioxide, with little or no oxygen.

Formation of early atmosphere

Volcanic activity released gases such as carbon dioxide, nitrogen, and water vapour.

Formation of oceans

Water vapour in the atmosphere condensed as the Earth cooled.

Decrease of carbon dioxide over time

It dissolved in oceans, was used by marine organisms, and became locked up in sedimentary rocks and fossil fuels.

Role of marine organisms in carbon dioxide removal

They used it to form shells and skeletons made of calcium carbonate.

Introduction of oxygen into the atmosphere

Photosynthesis by early algae and plants.

Word equation for photosynthesis

Carbon dioxide + water → glucose + oxygen

Effect of photosynthesis on atmosphere

It reduced carbon dioxide levels and increased oxygen levels.

Composition of fossil fuels

Remains of dead organisms buried under heat and pressure over millions of years.

Greenhouse gases

Gases that trap heat in the Earth's atmosphere by absorbing infrared radiation.

Examples of greenhouse gases

Carbon dioxide, methane, and water vapour.

Human activities increasing carbon dioxide levels

Burning fossil fuels and deforestation.

Human activities increasing methane levels

Cattle farming and rice cultivation.

Greenhouse effect

A natural process where greenhouse gases trap heat in the atmosphere and keep the Earth warm.

Importance of the greenhouse effect

It keeps the Earth warm enough to support life.

Global warming

A long-term rise in Earth's average temperature due to increased greenhouse gas levels.

Potential effects of global warming

Rising sea levels, extreme weather, changes in rainfall patterns, and impacts on biodiversity.

Carbon footprint

The total amount of carbon dioxide and other greenhouse gases emitted over the life cycle of a product, service, or event.

Ways to reduce carbon footprints

Using renewable energy, increasing energy efficiency, carbon capture, and planting trees.

Challenges in reducing carbon footprints

Because of economic, political, and practical challenges.

Pollutant

A substance released into the environment that causes harm.

Harmful gases from burning fuels

Carbon dioxide, carbon monoxide, sulfur dioxide, and oxides of nitrogen.

Problems caused by sulfur dioxide and nitrogen oxides

They contribute to acid rain and respiratory problems.

Acid rain

Rain that contains sulfuric or nitric acid, formed when sulfur dioxide or nitrogen oxides dissolve in water.

Effects of acid rain

It damages buildings, harms aquatic life, and kills plants.

Danger of carbon monoxide

It is colourless, odourless, and toxic — it prevents oxygen from being carried in the blood.