© Boardworks Ltd 20081 of 25. © Boardworks Ltd 20082 of 25

© Boardworks Ltd 20081 of 25



What are fossil fuels?

Coal, crude oil and natural gas are called fossil fuels.

Fossil fuels are found in the top layer of the Earth’s crust.

Most fossil fuels are made of chains of hydrogen and carbon atoms, called hydrocarbons.

Fossil fuels are so called because they are the remains of plants and animals that died and became trapped in the layers of sedimentary rocks millions of years ago.


As well as fuels, the fractions obtained from crude oil can be used to make many other useful substances, such as:

Why are fossil fuels used?

Fossil fuels provide more than 90% of the energy we need to produce electricity, power, heat and petrol, etc, for our homes and transport.

plastics, e.g. polythene and PVC

paints and dyes

fibres and fabrics

fertilizers and pesticides

perfumes and soaps

certain types of medicine.


How is coal formed?


Early stages of oil and gas formation

Oil and gas are also biological in origin. Millions of years ago, tiny animals lived in the sea. Like today, their ecosystem was dependent on heat and light from the Sun and photosynthesis by plants.

When they died, the animals fell into mud and sand at the bottom of the sea, but did not rot away.

Over millions of years they were buried deeper by the mud and sand.


Later stages of oil and gas formation

The temperature and pressure (caused by the weight of the sediments and deep burial) changed the mud and sand into rock, and the dead animals into crude oil and natural gas.

The oil and gas is extracted from the seabed or under the ground, by drilling oil wells.

Oil wells drilled at sea are supported by oil platforms.


Crude oil and fractional distillation

The oil that comes out of the ground is called crude oil. It cannot be used as it is, because it is a mixture of many different substances with different boiling points.

How can you separate a mixture of substances with different boiling points?

To separate out the useful substances, a process called fractional distillation is carried out.

big molecules boil at a high temperature

small molecules boil at a lower temperature


Fractional distillation


Fractional distillation: summary



How does the greenhouse effect work?


Global warming

Carbon dioxide is the main greenhouse gas involved in the warming of the Earth by the greenhouse effect.

An increase in the amount of greenhouse gases increases the amount of heat trapped in the atmosphere.

What are the effects of global warming?

Most scientists think that an increase in the greenhouse effect is making the Earth warmer and leading to global warming.

When fossil fuels are burned, they release carbon dioxide and other greenhouse gases, such as methane.


Effects of global warming

Most scientists predict that global warming will continue, and that it could cause major climate changes:

temperature – some areas may be warmer, others colder

coastal flooding – sea levels could rise as ice caps melt

rainfall – some areas may be wetter and others drier

plants – some crops may be able to grow better, and others, not at all.

Not all scientists agree about global warming though; some think that climate change is just a natural process on Earth.


Extracting fossil fuels

The extraction of fossil fuels from deep underground can cause several environmental problems:

land and water pollution – as fossil fuels are brought to the surface they can contaminate water supplies

disturbance – heavy machinery, roads and tankers are needed to extract and transport freshly-extracted fossil fuels, which can significantly disrupt rural areas

subsidence – poor mining techniques can cause land to collapse, and destroy habitats.


Fossil fuels – oil spills

Transporting raw fossil fuels can also have a damaging effect on the environment. Oil spills from ships or tankers are extremely hazardous to wildlife and the marine environment, and can take many months or years to clean up.

Wildlife that comes into contact with the oil become coated in it, making their feathers and fur less waterproof and insulating. This can make it difficult for them to fly or avoid predators.

Animals and birds are also at risk of ingesting the oil when they try to clean it off, causing damage to internal organs.


Can fossil fuels be re-used?

Fossil fuels are non-renewable; once a fossil fuel has been burnt it cannot be re-used. Why is this a problem?

Coal, oil and natural gas took millions of years to form, and are being used up much more quickly than they can ever be replaced.

Current estimates suggest that oil stocks might only last another 60 years, and coal and gas will run out within 150 years.

What is going to happen when we run out of fossil fuels?


Running out of fossil fuels

As fossil fuels begin to run out we will no longer be able to use our existing technology, appliances or transport networks.

As petrol becomes more scarce its price will rise. This in turn will increase the cost of almost all everyday goods and services, as well as making oil-based products more expensive to manufacture.

Most economists predict that unless sustainable alterative fuel sources are developed, lack of fossil fuels could lead to economic depression, mass unemployment and famine.


Carbon footprint

The amount of carbon dioxide produced by carrying out activities in everyday life is sometimes called our carbon footprint.

Here are the average carbon footprints of people in some different countries.

USA

Canada

Australia

UK

Egypt

China

Country CO2 emissions*

21

20

16

10

4

2

0.3Bangladesh

What do you notice about the size of the CO2 emissions from each country?


Reducing your carbon footprint

By reducing your carbon footprint you can help produce less carbon dioxide, and reduce the demand for fossil fuels.

What are some easy ways to reduce your carbon footprint?

hang washing outside to dry rather than use a tumble dryer

turn off lights, computers, etc, when not in use

walk or ride a bicycle, rather than drive

only run the dishwasher with a full load

turn down the central heating by 1 °C.

Why is it important to start reducing your carbon footprint now, rather than in 50 years’ time?


The greenhouse effect: summary



What do chemists do?

Chemists carry out chemical reactions. Most of the time their aim is to make new substances that can improve people’s lives.

Can you think of some examples of beneficial substances that have been developed by chemists?

medicines that prevent or cure diseases

materials for smaller computer chips

fertilizers that increase crop yield

cosmetics, soaps and make-up

anti-rust paint

cleaner fuels.


Careers in chemistry – fuel researcher


Careers in chemistry

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© Boardworks Ltd 20081 of 25. © Boardworks Ltd 20082 of 25