Chemistry 4.9.1.1

The Atmosphere

% of nitrogen in our current atmosphere

80

% of oxygen in our current atmosphere

20

% of carbon dioxide in our current atmosphere

0.04

% of argon in our current atmosphere

0.9

Formation of early atmosphere

Frequent volcanic eruptions released gases

Main gases in the early atmosphere

Carbon dioxide, methane, ammonia and water vapour

How oxygen levels increased

The evolution of plants caused carbon dioxide to be absorbed and changed into oxygen by photosynthesis, which is released

How carbon dioxide levels decreased

Carbon dioxide is absorbed by plants for use in photosynthesis. It dissolves into the oceans and becomes locked up into sedimentary rocks/fossil fuels

How nitrogen levels increased

Ammonia + Oxygen → Nitrogen + Water

Why nitrogen levels remain constant

Nitrogen isn't a very reactive gas

Three greenhouse gases

Carbon dioxide, methane and water vapour

Cause of greenhouse effect

1. Electromagnetic radiation from the Sun passes through the Earth's atmosphere. 2. The Earth absorbs it and radiates infrared. 3. Some infrared is absorbed by greenhouse gases. 4. The atmosphere warms up.

Global warming

Gradual increase in the average temperature of the Earth

Carbon footprint

The total amount of carbon dioxide produced directly and indirectly by human activities (in tonnes of CO₂)

Climate change

Large-scale, long-term shift in the Earth's weather patterns or average temperatures

How human activity causes global warming

Increased levels of carbon dioxide in the atmosphere cause more heat radiation to be trapped and raise Earth's average temperature

Three effects of climate change

Polar ice melts, sea levels rise, and low-lying land floods

Three steps to reduce carbon footprint

Use of alternative fuels (e.g. hydrogen), reduce/reuse/recycle, and use public transport/walk

How carbon dioxide is formed

Complete combustion of fuels

How carbon monoxide is formed

Incomplete combustion of fuels

How carbon particulates are formed

Incomplete combustion of fuels

How sulphur dioxide is formed

Sulphur impurities in fuels react with oxygen during combustion

How nitrogen oxides are formed

Nitrogen and oxygen from the air react in the hot engine

Environmental effect of carbon dioxide

Global warming

Environmental effect of carbon monoxide

Breathing difficulties

Environmental effect of carbon particulates

Global dimming and cancer

Environmental effect of sulphur dioxide

Acid rain (kills fish/plants and erodes limestone)

Environmental effect of nitrogen oxides

Acid rain and respiratory problems