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Unit 7
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- 2. 2 UNIT 7 ENERGY CONTENTS 1. ENERGYAND ITS SOURCES 1.1. What is energy? 1.2. Energy sources 2. RENEWABLE ENERGY SOURCES 2.1. The Sun 2.2. The wind 2.3. The water 3. NON RENEWABLE ENERGY SOURCES 3.1. Coal 3.2. Petrol 4. ENERGY IN OUR HOUSES 4.1. Electric energy 4.2. Gas energy 4.3. Saving energy
- 3. 3 1. ENERGY 1.1. WHATIS ENERGY? Energy is what makes things move and change their properties. To light a bulb electric energy is needed; and to move a car fuel is needed. People need food energy to do their everyday activities: study, run, play… 1.2. ENERGY SOURCES Energy can have different origins. Energy sources are the ones we get energy from: the Sun, petrol, coal, water… Energy sources can be divided into two groups: - Renewable energy sources. They are almost endless; like the Sun, the water and the wind. - Non renewable energy sources. They are limited; like petrol, coal and gas. These sources become exhausted as we use them.
- 4. 4 2. RENEWABLE ENERGYSOURCES 2.1. THE SUN Solar energy is produced by the Sun. The Sun is our main energy source, most changes on Earth depend on the Sun energy. Plants, animals and people need the Sun heat and light to live. Nowadays, Sun energy is also used to produce electric energy and keep houses warm (with radiators). With solar panels Sun energy is transformed into electric energy and with accumulators water for radiators gets hot. 2.2. THE WIND Wind energy is the one produced by moving air. This energy moves windmills and sailing boats. In the past windmills were used to grind grain, like flour. Nowadays there are modern windmills (called wind turbines) that transform wind in energy. 2.3. THE WATER Energy produced by moving water is called hydraulic energy. Rivers´ water was used to move mills and grind wheat and corn. Nowadays the water of some rivers is collected in reservoirs to produce electric energy.
- 5. 5 3.NON RENEWABLE ENERGYSOURCES 3.1. COAL Coal is a black rock formed by trees and plants, which were death millions of years ago. It is underground and there are mines to extract it. When coal burns it produces a great amount of heat and for many years it has been used in kitchens to cook and in stoves to heat houses. Afterwards coal was used to improve means of transport and in industry to move machines. Coal mines are disappearing, and as it is a very contaminating energy it is being substituted by other energy sources. 3.2. PETROL It is a dark liquid that was formed by small organisms which lived in the sea millions of years ago. It is very deep under the Earth´s surface. To extract petrol there are deep wells in the sea and in the land. Petrol is transported with very big pipes or ships. When these ships have accidents they contaminate a lot. Petrol and its derivatives (oil, gas) are the most common energy source nowadays.
- 6. 6 4. ENERGY INHOUSES 4.1. ELECTRIC ENERGY Electric energy we use in our houses comes from: - Hydroelectric centrals, which use water movement to produce energy. - Thermic centrals, where heat from fuel is used to produce energy. Produced energy gets to our houses by the electric net. 4.2. GAS ENERGY In our houses we can also use gas to get energy. There are two kinds of gas: - Natural gas is found, as petrol, in natural deposits and is transported by pipes. - Butane gas comes from petrol, it is made with petrol by humans. Natural and butane gases are combustibles that produce a great amount of heat when they burn. Heat is used to heat houses, to cook or to heat water we use to take showers. 4.3. SAVING ENERGY We don´t have to waste energy. We can follow these advises: - Switch of the room´s light if you are not in. - Don´t leave electrical devices (TV or music) on when you aren´t using them. - Don´t leave fridge´s door opened for a long time.