Page 164 - Science Coursebook
P. 164

11.2  Fossil fuels







                An energy resource is anything from which we can obtain              nuclear
                energy. The pie chart shows the energy resources we use, and
                the fraction of our total needs each type contributes.     renewables                       oil

                You can see that most of the energy we use comes from
                fossil fuels. These are coal, oil and natural gas.


                   Question                                                      gas
                   1   a   Which fossil fuel is used the most as an
                         energy resource?
                     b   Use the pie chart to estimate the fraction of our                            coal
                         energy which comes from fossil fuels.              The energy resources we use around
                                                                            the world.
                Chemical stores
                In Stage 7 Unit 10 you learnt about how energy changes
                from one form to another. Fossil fuels are stores of chemical
                energy. The energy is released when the fuel is burnt.

                For example, in a car engine, petrol and air are mixed
                together. A spark ignites the mixture and it burns. The
                energy released makes the car move forward.

                Fossil fuels are useful because they are very concentrated
                stores of energy. It takes only a minute or two for a driver to
                put 50 litres of petrol into the car’s tank. Then it is ready to

                travel 1000 km or more.                                     Refuelling a taxi with petrol at a filling
                                                                            station in Borneo.
                   Questions

                   2   What name is given to the energy of a moving car?
                   3   Many people use oil to heat their homes. Draw a
                     diagram to show this energy change.


                Where the energy came from
                Fossil fuels are found underground. Coal formed from the
                remains of plants that died millions of years ago. Oil and
                gas formed from the remains of sea creatures.
                Those living organisms gained their energy originally from
                sunlight. So, when we burn fossil fuels, we are making use
                of the energy of sunlight which fell on the Earth a very
                long time ago.


                   Question
                   4   Why is it wrong to say that fossil fuels are stores
                     of light energy?                                       In some parts of the world, oil and gas
                                                                            are extracted from under the seabed.

               162     11 Energy




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