'the sun is the principal source of energy.... we can neither feel nor see' comment on it.
Answers
To be aware of the different forms of energy and the time frame necessary for the development of these energy forms.
OBJECTIVE:
1. The student will become familiar with different forms of energy.
2. The student will understand the sources of energy.
3. The student will acquire an understanding of the history of various sources of energy.
LESSON / INFORMATION:
Are energy sources renewable or nonrenewable? You can decide for yourself. If a source of energy is replaced as we use it, so that we can never use it up, it is called renewable. If there is a definite, limited supply of a source of energy, and it cannot be replaced, it is called nonrenewable. This is an important idea, because it helps us to decide how we should use each of our many sources of energy.
Energy is all around us and comes from many sources. One of the most important sources of energy is the sun. The energy of the sun is the original source of most of the energy found on earth.
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We get solar heat energy from the sun, and sunlight can also be used to produce electricity from solar (photovoltaic) cells.
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The sun heats the earth's surface and the Earth heats the air above it, causing wind.
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Water evaporated by the sun forms clouds and rain to give us flowing streams and rivers. Both wind and flowing water (hydropower) are sources of energy.
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So you see, the sun is the source of many kinds of energy found in nature. These kinds of energy are around us all the time. They are produced quickly, and replace themselves constantly as we use them. For this reason we say they are renewable.
The sun's energy can also be stored. Plants store energy from the sun as they grow. Fruits, vegetables and wood from trees, for example, all contain stored solar energy. We call it biomass energy, from "bio" for "life" or "living". These kinds of energy are also renewable, but of course it takes longer to grow a plant or a tree than it does to get heat directly from sunlight.
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When energy is stored in a material, we call that material fuel. Food and wood are biomass fuels. When you have old biomass that has become concentrated, you have what we call "fossil fuel".
THE FORMATION OF FOSSIL FUELS
Fossil fuels are found deposited in rock formations. They were formed there between 350 million and 50 million years ago. The processes by which they were formed are not totally understood. Decayed remains of ancient plants and/or animals were buried by sediments. Through the action of heat and pressure over millions of centuries, they were chemically changed. Coal, oil, and natural gas are the results.
Coal was formed from the remains of ferns, trees, and grasses that grew in great swamps 345 million years ago. These remains formed layers as they sank under the water of the swamps. The plant material partially decayed as these layers formed beds of peat, a soft brown substance that is up to 30% carbon. Peat is the earliest stage of coal formation.
Shallow seas later covered the swamps and slowly deposited layers of sand and mud over the peat. These sediments exerted pressure on the peat over thousands of years. Slowly, chemical changes took place transforming it into lignite or brown coal, which is about 40% carbon. Millions of years later, increasing pressure and heat changed lignite into bituminous or soft coal (about 66% carbon) and finally into anthracite or hard coal (over 90% carbon).
Oil and natural gas are also found in beds of sedimentary rock. The sediments were deposited by shallow seas millions of years ago. The remains of plants and animals living in the seas settled to the bottom and were buried under layers of sediment. These layers were subjected to heat and pressure over millions of years. The sediments were transformed into beds of rock, and the plant and animal remains underwent slow chemical change and formed oil and natural gas.
As you can see, the fossil fuels take millions of years to form. They cannot be replaced quickly. In fact, in terms of our lifetime they cannot be replaced at all. For that reason we call them nonrenewable.
Explanation:
One of the most important sources of energy is the sun. The energy of the sun is the original source of most of the energy found on earth. We get solar heat energy from the sun, and sunlight can also be used to produce electricity from solar (photovoltaic) cells.
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