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Download Science Year 7 Learn Sheet DC4 – Energy
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Energy from the sun. Energy transfers and stores. Energy from food. Most of the energy resources we use store energy that originally came from the Sun. Only geothermal power, nuclear power and tidal power do not depend on energy from the Sun. • • • • • • • • Humans and other animals need energy to live. The energy resource for our bodies is the energy stored in food. We need to choose our food so that we get the right amount of energy. The unit for measuring energy is the joule (J). There is a lot of energy stored in food, so we usually measure the energy in food using kilojoules (kJ). 1 kJ = 1000 J • • • • Renewable energy • • • • • • • • include solar, wind, tidal, wave, biofuels, geothermal and hydroelectricity do not produce harmful gases or contribute to global warming are often more expensive than using fossil fuels will not run out are not always available. Hydroelectricity, geothermal energy and biofuels are available at any time. Tidal power is not available all the time, but we can predict when it will be available. Energy from solar, wind and waves is only available some of the time. • Key words: 1. 2. 3. 4. 5. 6. 7. 8. Energy: Something that is needed to make things happen or change. Joule (J): The unit for measuring energy. Kilojoule (kJ): There are 1000 joules in 1 kilojoule. Chemical energy: A name used to describe energy when it is stored in chemicals. Food, fuel and batteries all store chemical energy. Elastic potential energy: A name used to describe energy when it is stored in stretched or squashed things that can change back to their original shapes. Another name for strain energy. Gravitational potential energy: A name used to describe energy when it is stored in objects in high places that can fall down. Thermal energy: A name used to describe energy when it is stored in hot objects. The hotter something is the more thermal energy it has Fossil fuel: Coal, oil and natural gas – all fuels that were formed from the remains of dead plants and animals. Fossil Fuels • • • • • • are made from plants and animals that were trapped in mud and rocks millions of years ago include coal, oil and natural gas are non-renewable (they take millions of years to form, and so our supplies will run out) produce gases that cause pollution and global warming when burnt are relatively cheap to obtain originally got their energy from the Sun. The plants that became coal, oil and natural gas got their energy from the Sun, and the animals that became oil and natural gas got their energy from plants, which got their energy from the Sun. • Energy can be transferred by: ● heating ● light ● sound ● electricity ● forces. the chemicals in food, fuels and batteries chemical energy moving objects kinetic energy hot objects thermal energy objects that are stretched, squashed or twisted strain energy or elastic potential energy objects moved to high places gravitational potential energy inside the particles that everything is made up from nuclear energy or atomic energy Energy is not used up. It can be transferred and stored in different ways, but it cannot be created or destroyed. This is called the law of conservation of energy Fuels. • Fuels store energy, and this energy is transferred when the fuels burn. • Burning fuels are used to heat things. • Nuclear fuel is also non-renewable. Nuclear power stations produce dangerous waste materials. • Electricity is not a fuel. It has to be generated using other energy resources. Revision Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. Name all the types of energy you have studied in this unit. For each one, state one place it could be observed. What does ‘conservation of energy’ mean? What is the rule for conservation of energy? Draw an energy transfer diagram for a toaster. (Ext: label the useful and wasted energy). Use this diagram to explain what efficiency is. Name 2 renewable energy sources. Explain the advantages of using renewable energy. Explain what renewable means. Name 2 non-renewable energy sources. Explain what non-renewable means. What are fossil fuels? Give the definition and some examples. Why are fossil fuels bad for the environment? Explain at least 3 reasons. Explain how geothermal power stations work – include a diagram with your answer. Explain how hydroelectric power stations work – include a diagram with your answer. Revision Questions 1. Name all the types of energy you have studied in this unit. 2. What does ‘conservation of energy’ mean? 3. Draw an energy transfer diagram for a toaster. (Ext: label the useful and wasted energy). 4. Name 2 renewable energy sources. Explain the advantages of using renewable energy. 5. Name 2 non-renewable energy sources. 6. What are fossil fuels? 7. Why are fossil fuels bad for the environment? 8. Explain how geothermal power stations work – include a diagram with your answer. 9. Explain how hydroelectric power stations work – include a diagram with your answer.