Date post: | 15-Jan-2016 |
Category: |
Documents |
Upload: | alfred-barton |
View: | 454 times |
Download: | 51 times |
© Boardworks Ltd 20081 of 25
© Boardworks Ltd 20082 of 25
© Boardworks Ltd 20083 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.
© Boardworks Ltd 20084 of 25
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.
© Boardworks Ltd 20085 of 25
How is coal formed?
© Boardworks Ltd 20086 of 25
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.
© Boardworks Ltd 20087 of 25
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.
© Boardworks Ltd 20088 of 25
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
© Boardworks Ltd 20089 of 25
Fractional distillation
© Boardworks Ltd 200810 of 25
Fractional distillation: summary
© Boardworks Ltd 200811 of 25
© Boardworks Ltd 200812 of 25
How does the greenhouse effect work?
© Boardworks Ltd 200813 of 25
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.
© Boardworks Ltd 200814 of 25
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.
© Boardworks Ltd 200815 of 25
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.
© Boardworks Ltd 200816 of 25
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.
© Boardworks Ltd 200817 of 25
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?
© Boardworks Ltd 200818 of 25
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.
© Boardworks Ltd 200819 of 25
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?
© Boardworks Ltd 200820 of 25
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?
© Boardworks Ltd 200821 of 25
The greenhouse effect: summary
© Boardworks Ltd 200822 of 25
© Boardworks Ltd 200823 of 25
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.
© Boardworks Ltd 200824 of 25
Careers in chemistry – fuel researcher
© Boardworks Ltd 200825 of 25
Careers in chemistry