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2 HOW CAN THE SUN S ENERGY BE USED? Most of the living things on Earth obtain their energy directly or indirectly from the Sun. Humans consume solar energy by eating plants and animals. Humans also build devices to capture energy from the Sun and put it to practical use. Two types of solar heating systems: Active Solar Heating Passive Solar Heating Solar Cells- generate an electric current from sunlight.

3 WHAT ARE FOSSIL FUELS? Scientists believe that the plants in swamps became buried as they died. Over time the plants remains were covered by sand and other mineral matter. Eventually heat and pressure converted the plant remains into a mineral called coal. Oil and natural gas came from the remains of tiny, oceandwelling plants and animals are buried under mud and sand in the same way. Coal, oil, and gas give off large amounts of heat when burned, so they make very good fuels. They are called fossil fuels because they are formed from ancient plants and animals. Because they take millions of years to form, they are called nonrenewable resources.

4 HOW CAN MODERN PLANT AND ANIMAL MATTER GIVE US ENERGY? Biomass Conversion- New methods allow us to change both plant and animal materials into high-quality fuels. The fuels from biomass conversion are examples of renewable resources, we can make more of the resources and use them again and again. Examples: Fermenting corn and sugar creates ethyl alcohol which is a good fuel that can be mixed with gasoline. Bacteria in landfills and animals create methane, which is the main ingredient in natural gas.

5 WHAT IS NUCLEAR FISSION? Nuclear Reaction- a change in the number of protons produces a different atom. Nuclear Fission- the splitting of a nucleus into two pieces. The nucleus can be split when struck by a slow moving electron. Neutrons and energy are produced. If enough atoms are presents, the split atom can cause other atoms to split. Chain Reaction- a reaction that is kept going by the products of the reaction. The energy released is much greater than the energy used to start the reaction.

6 WHAT IS NUCLEAR FUSION? Nuclear Fusion- energy is released when nuclei with smaller masses merge to make a nucleus with a larger mass. Some neutrons don t fuse in the reaction. When this happens, a lot of energy is released. This reaction only occurs at very high temperatures. The conditions are perfect for this reactions in cores of starts. The reactions create vast amounts of energy and allow stars to shine for billions of years.

7 WHICH IS BETTER, FISSION OR FUSION? Nuclear fission reactors produce electricity to many regions of the US and Europe. The reactors are quiet, do not pollute the atmosphere, and help conserve fossil fuels. Uranium is used in the nuclear fission reactors to start the reaction. This can be mined in the Earth. The reactors has one big problem. The process of nuclear fission creates a lot of toxic waste that is hard to dispose of. A nuclear fusion reaction does not have the same problems. It produces less waste. Helium is used in the reaction which is easier to obtain. We have not yet built a successful fusion reactor. ll4ai4

8 HOW CAN WE CAPTURE ENERGY FROM WIND? Wind is a form of solar energy. Wind is caused by uneven heating of Earth s surface by the Sun. Windmills have been used for centuries and wind turbines have been adapted for electricity. Wind turbines convert wind into electricity. Wind power is clean and will never be used up, but some people don t like the noise and appearance of the turbines.

9 HOW CAN FALLING WATER GIVE US ENERGY? Hydroelectricity- when the flow of water produces electricity. It is a form of solar energy. The Sun warms the water in oceans and lakes, causing it to evaporate. It then becomes rain in higher elevations. As water runs downhill and gains kinetic energy. This energy can be tapped for hydroelectricity. The US gets 15% of its electricity from hydroelectricity. It causes little pollution and it will always be available if it rains or snows. The number of rives that support large dams is small. Building dams are expensive and harmful to the surrounding environment.

10 HOW CAN FOSSIL FUELS BE USED TO MAKE ELECTRICITY? When fossil fuels are burned, they combine with oxygen in the air to make water, carbon dioxide, and heat. This creates electricity.