9. Chemistry of the Atmosphere

State the length of time that the proportions of different gases in the atmosphere have been much the same as they are today

For 200 million years

Describe the components of the atmosphere and the relative proportions

80% nitrogen
20% oxygen
Small proportions of various other gases, including carbon dioxide, water vapour and noble gases.

Explain why evidence for the early atmosphere is limited

Because of the very long time scale of 4.6 billion years

Describe one theory for the formation of the early atmosphere during the first billion years of the Earth's existence .

There was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans

State which planets have similar atmospheres to Earth's very early atmosphere

It may have been like the atmosphere of Mars and Venus today

Describe the current scientific ideas about the componentes of the early Earth's atmosphere

It may have consisted of mainly carbon dioxide with little or no oxygen gas.
Volcanoes also produced nitrogen which gradually built up in the atmosphere.
Three may have been small proportions of methane and ammonia.

What reduced the amount of carbon dioxide in the atmosphere?

Carbon dioxide dissolved in the oceans when they formed.
Carbonates were precipitated producing sediments.
Carbon dioxide was also decreased by the formation of sedimentary rock and fossil fuels that contain carbon.

Describe the role of algae and plants in changing the Earth's atmosphere from 2.7 billion years - 200 million years ago

Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis.
Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.

State when oxygen first appeared in the atmosphere

About 2.7 billion years ago

State what had to happen before animals could evolve

Oxygen levels had to gradually increase to a level that enabled animals to evolve

Describe the role of greenhouse gases in supporting life on Earth

Greenhouse gases maintain temperatures on Earth high enough to support life

List three greenhouse gases

Water vapour, carbon dioxide and methane

Explain how carbon dioxide and methane have increased due to human activity

Carbon dioxide has increased due to combustion of fossil fuels and deforestation.
Methane has increased due to planting rice fields and cattle farming.
Deforestation reduces photosynthesis and increases carbon dioxide.
Destruction in peat bogs releases carbon dioxide.

The greenhouse effect

Radiation from the sun has a short wavelength which passes through the atmosphere.
Radiation from objects on the Earth's surface emit a longer wavelength absorbed by greenhouse gases
The night time temperature on Earth is increased, allowing life to survive at night

Explain why scientists believe that human activities will cause the temperature of the Earth's atmosphere to increase at the surface

They have peer reviewed evidence

Describe what causes global climate change

An increase in average global temperature is a major cause of climate change

Describe five effects of global climate change

Sea levels rising
Extreme weather events
Changes in the amount and time of rainfall
Changes to ecosystems and habitats
Polar ice caps melting

Define carbon footprint

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

Describe how the carbon footprint can be reduced

The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane. Going vegan, other transport alternatives to driving

State a major source of atmospheric plants

The combustion of fuels is a major source of atmospheric pollutants

State what most fuels contain

Carbon, hydrogen and may also contain sulphur

State what gases released into the atmosphere when a fuel is burned

Carbon dioxide, water vapour, carbon monoxide, sulphur dioxide, oxides of nitrogen

Describe how carbon monoxide is produced by burning fuels

Incomplete combustion of fuels

Describe how soot (carbon particles are produced by burning fuels

Incomplete combustion of fuels

Describe how soot (carbon particles are produced by burning fuels

Incomplete combustion of fuels especially in Diesel engines

Describe how sulphur dioxide is produced by burning fuels

Sulphur impurities in the fuel react with oxygen from the air

Describe how oxides of nitrogen are produced by burning fuels

Nitrogen in the air is heated near an engine and it reacts with ocygen

Describe carbon monoxide and explain why it is not easily detected

Carbon dioxide is a toxic gas. It is colourless and odourless and so is not easily detected

Describe what the effects of sulphur dioxide and oxides of nitrogen cause

Sulphur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain

Describe what particulates (soot and unburnt hydrocarbons) cause

Particulates cause global dimming, respiratory problems and have the potential to cause cancer.

Describe how sulphur dioxide emissions can be reduced

Using reduced sulphur fuels
Dissolving some of the sulphur dioxide in solutions before it's released into the atmosphere.