Burning fossil fuels Flashcards
What are the fossil fuels? How were they formed?
The fossil fuels are coal, oil and natural gas. They were formed from the remains of living organisms millions of years ago.
What is crude oil? (3)
Crude oil is a fossil fuel, and is a mixture of hydrocarbons of different lengths. It is made up of dead plants and animals that, over millions of years, have been squashed by sedimentary rock and heated up and have eventually turned into oil.
What is complete combustion? (3)
Fuels burn when they react with the oxygen in the air. The hydrogen in hydrocarbons is oxidised to water.
When there is enough oxygen, the hydrocarbon is completely combusted and there are no excess products.
What is the word equation for complete combustion?
Hydrocarbon + Oxygen => Water + Carbon dioxide
What is incomplete combustion? (3)
When there is insufficient oxygen, the hydrocarbon has not been fully combusted and there are excess products.
The hydrogen is still oxidised to water, but instead of carbon dioxide, we get carbon monoxide. Particles of carbon, seen as soot or smoke, are also released.
What is the word equation for incomplete combustion?
Hydrocarbon + less oxygen => Water + Carbon (soot) + Carbon monoxide
How is sulphur dioxide released when fossil fuels are combusted? (2)
Most hydrocarbon fuels naturally contain some sulphur compounds. When the fuel burns, the sulphur it contains is oxidised to sulphur dioxide.
What gases can be released into the atmosphere when fossil fuels are combusted? (4) Why is this a problem?
Water vapour
Carbon dioxide
Carbon monoxide
Sulphur dioxide
These gases may be harmful to the environment.
What is sulphur dioxide? What does it cause? (4)
Sulphur dioxide is released when gases with sulphur compounds burn. It is a gas with a sharp, choking smell. When sulphur dioxide dissolves in water in clouds, it makes rain more acidic than usual. This is called acid rain.
What are the effects of acid rain? (5)
Acid rain reacts with metals and rocks, such as limestone. As a result, buildings and statues can be damaged.
Acid rain damages the waxy layer on the leaves of trees and makes it more difficult for trees to absorb the minerals they need for healthy growth. They may die as a result.
Acid rain also makes rivers and lakes too acidic for some aquatic life to survive.
How can acid rain be reduced? (3, 2)
Sulphur dioxide can be removed from waste gases after combustion of the fuel. This happens in power stations.
The sulphur dioxide is treated with powdered limestone to form calcium sulphate.
This can be used to make plasterboard for lining interior walls, so turning a harmful product into a useful one.
Sulphur can also be removed from fuels at the oil refinery. This means the oil is more expensive to produce, but it prevent sulphur dioxide from being released into the atmosphere.
