Energy Comes in Many Forms
Can you imagine a world without energy? You wouldn’t be able to play computer games, ride a bicycle, or talk on the phone. Cars and trucks wouldn’t move. Lights wouldn’t shine. Plants wouldn’t grow. Without energy, nothing would happen!
Energy is the ability to change or move matter.
Just about everything you see, hear, and feel depends on energy. Energy comes in many forms.
Chemical energy is energy that is released by a chemical reaction. The food you eat contains chemical energy that is released when you digest your meal. Wood, coal, gasoline, and natural gas are fuels that contain chemical energy. When these fuels are burned, the chemical energy is released as heat.
Radiant energy is energy that can move through empty space. The sun and stars are very powerful sources of radiant energy. The heat and light given off by lightbulbs and campfires are also forms of radiant energy.
Mechanical energy moves objects from place to place. You use mechanical energy when you kick a ball or turn the pedals of a bicycle. Other examples of mechanical energy include water flowing in a stream or tires rolling down a road.
Electrical energy comes from the electrons within atoms. It can be created at a power plant or inside a battery, and can power everything from remote-controlled cars to refrigerators. Lightning and static electricity are also forms of electrical energy.
Nuclear energy is energy contained in the nucleus at the center of an atom. Nuclear energy is released when nuclei are split apart into several pieces, or when they are combined to form a single, larger nucleus.
An atom is the smallest unit of matter. Scientists so far have found 112 different kinds of atoms. Everything in the world is made of different combinations of these atoms. Every atom has a nucleus in the center. Tiny particles called electrons travel around the nucleus. The flow of electrons produces electricity.
Energy Can Move and Change
When you ride a bicycle, you transfer mechanical energy from your legs to the pedals. The pedals transfer the energy to the bicycle gears, which transfer the energy to the tires. The rolling tires move the bike along the street.
When a cat sits on a sunny windowsill, radiant energy from the sun is transferred through the window to the cat’s fur. The radiant energy heats up the fur and the cat’s body.
Energy can be transformed, or changed, from one form to another.
Suppose you eat a hamburger for lunch. Later that afternoon, you run in a race. Your body, through the digestive process, changes the chemical energy in the hamburger to the mechanical energy of your arms and legs so you can run.
A toaster changes electrical energy to heat. Electricity flows into the toaster’s heating elements, which are made of wires. The flow of electricity heats the wires. Heat from the wire is transferred to the slice of bread. Up pops your toast!
A car changes the chemical energy of gasoline to the mechanical energy of wheels turning. Inside a car’s engine, gasoline is burned in small bursts. Each burst of energy creates motion in the engine’s crankshaft and other moving parts. This motion is transferred to the wheels of the car, making them turn.
Many Different Energy Resources Can Be Used to Make Electricity
You probably know that most of the electricity you use is produced in a power plant and travels to your home and school through special wires. But do you know what energy sources are used to run power plants?
Energy resources can be divided into two categories: nonrenewable and renewable.
A nonrenewable resource is a resource that can be used up. Fossil fuels, which include coal, oil, and natural gas, are nonrenewable because it took millions of years for them to form. Once we use up our fossil fuels, they will be gone for good.
Many power plants use fossil fuels. The fossil fuel is burned to produce heat, which is used to make steam. The steam is then used to turn the blades of a turbine.
Some power plants run on nuclear power, which is another nonrenewable resource.
Nuclear power plants rely on uranium, a type of metal that is mined from the ground and specially processed. Heat released from splitting uranium atoms is used to convert water into steam that turns turbines.
A renewable resource is fairly easy to replace. Renewable energy resources include wood, wind, sunshine, geothermal energy, biomass, and water stored behind dams in lakes and reservoirs. Electricity can be produced using several kinds of renewable resources.
Biomass is material that is formed from living organisms, such as wood or agricultural wastes. Biomass can be burned to produce electricity, or be converted to a gas and used for fuel.
Geothermal energy uses hot water or steam from deep beneath the earth’s surface to produce electricity.
Hydroelectric power plants use the energy of falling water to spin generator turbines.
Solar energy can also be used to produce electricity. Solar cells change the radiant energy of the sun into electrical energy. Some calculators and portable radios are powered by solar cells. Solar panels, or modules, placed on a rooftop can supply electricity to the building below.
Energy Resources Today
The energy resources people use today can be divided into two categories: nonrenewable and renewable.
Nonrenewable resources cannot be replenished. We have limited supplies of them, and when these supplies are gone we will not have any more.
Fossil fuels were formed from the fossilized remains of tiny plants and animals that lived long ago. Most electricity used in the world is generated from power plants that burn fossil fuels to heat water and make steam. The highly pressurized steam is directed at turbine blades to make them spin.
The three forms of fossil fuels are coal, oil, and natural gas.
- Coal is a hard, black, rock-like substance made up of carbon, hydrogen, oxygen, nitrogen, and sulphur. There are three main types of coal: anthracite, bituminous, and lignite. The precursor to coal, called “peat,” is still found in many countries and is also used as an energy source. Coal is found in many parts of the U.S. and throughout the rest of the world.
- Oil is a liquid fossil fuel, sometimes also called petroleum. It is found underground within porous rocks. To obtain oil, companies drill down to deposits deep below the earth’s surface using oil rigs. More than half of all the oil we use in the U.S. comes from outside our country—most of it from the Middle East.
- Natural gas is made up primarily of a gas called methane. Methane gas is highly flammable and burns very cleanly. Natural gas is usually found underground along with oil. It is pumped up and travels through pipelines to homes and businesses. Natural gas supplies are abundant from sources in the U.S. and Canada.
Nuclear power uses heat released from splitting atoms to convert water into steam that turns turbines. Nuclear power plants rely on uranium, a metal that is mined and specially processed. Fuel rods containing uranium are placed next to each other in a machine called a nuclear reactor. The reactor causes the uranium atoms to split and in so doing, they release a tremendous amount of heat.
Renewable energy resources can be replenished in a short period of time, so they will never be all used up. Energy companies around the country are using renewable resources more and more to generate electricity.
Biomass is organic matter, such as agricultural wastes, wood chips, and bark left over when lumber is produced. Biomass can be burned in an incinerator to heat water to make steam, which turns a turbine to make electricity. It can also be converted into a liquid or gas, which can be burned to do the same thing.
Biomass includes energy crops like wood, straw, and other crops grown primarily for use as a fuel. Energy crops are renewable, but some, like trees, take a long time to grow.
Farmers can grow trees on some of their land instead of wheat or other kinds of food. The wood is harvested regularly, cut into small chips and burned to provide heat or run small electric power plants.
Geothermal energy is steam (or hot water that has been converted to steam) from deep inside the earth. Our planet’s interior is very hot—at its core, 4,000 miles deep, temperatures may reach over 9,000°F. This heat is continuously conducted from the earth’s core to the surrounding layer of rock, the mantle.
There are some places around the earth where magma (hot molten earth from the mantle) pushes up through cracks into the crust near the earth’s surface. Magma can heat nearby rock and water as hot as 700° F. Some of this hot water reaches the earth’s surface as hot springs or geysers, and some stays trapped deep underground in cracks and porous rocks. This hot water can be used directly or converted into steam to turn turbines that generate electricity. (The word “geothermal” comes from the Greek words geo, for earth, and therme, for heat. So geothermal means “earth heat.”)
Hydrogen is a colorless, odorless gas. Hydrogen can be converted into electricity through a chemical reaction in a device called a fuel cell. Converting hydrogen into electricity produces no pollution—only water and heat.
If the hydrogen comes from a renewable resource like landfill gas, fuel cells are considered renewable. However, if it comes from a nonrenewable resource like fossil fuels, fuel cells are considered nonrenewable.
Today, NASA uses hydrogen fuel cells to convert hydrogen into electricity for astronauts. There are already some cars that run on hydrogen. In the future, hydrogen will be used to fuel vehicles and airplanes and to provide electricity to buildings.
Hydropower uses the power of falling water to generate electricity. Water that is stored behind a dam is released and directed through tubes to flow against turbine blades and make them turn. Most hydropower facilities are found in hilly or mountainous areas. Hoover Dam is the most famous hydroelectric facility in The USA.Ocean energy is a form of hydropower. Oceans cover more than 70% of the earth’s surface, making them the world’s largest solar collectors. The ocean stores thermal (heat) energy, which can be used to generate electricity using special turbine generators.
The energy of the ocean’s waves and tides can also be used to generate electricity with dams that force ocean water through turbines. This is called tidal energy, or wave power. The world’s first wave power station is on the Scottish island of Islay. It generates enough electricity for about 400 homes. Scientists and engineers around the world are working on systems to use the ocean’s energy on a large scale.
Every day, more solar energy falls to the earth than all the people on earth could use in 27 years! Special panels of solar cells, or modules, can capture sunlight and convert it directly into electricity. These panels are known as photovoltaic, or PV. (“Photo” is Greek for light, and “voltaic” pertains to electricity.) The electricity they produce can be used right away, fed into the power grid for others to use, or stored in a battery so it is also available on cloudy days.
Most wind power is produced at wind farms, which are large groups of turbines in consistently windy locations. A very large wind farm can generate enough electricity for all the homes in a city of about one million people. Small wind turbines can be used for individual homes, businesses, and boats. They can be used to pump water, or the electricity can be stored in large batteries for use at another time.
To finish, this table will clarify the contents explained before:
|Energy-Using Item||Energy Source||Form(s) of Energy|
|space heater||electricity||electrical; radiant|
|fireplace||wood or natural gas||chemical; radiant|
|kitchen stove||natural gas or electricity||chemical; radiant; electrical|
|ceiling fan||electricity||electrical; mechanical|
|portable radio||battery||chemical; electrical|
|alarm clock||battery or electricity||chemical; electrical|
|CD or DVD player||electricity||electrical|
|portable CD player||battery||chemical; electrical|
|portable calculator||solar cell||radiant|
|clothes washer||electricity||electrical; mechanical|
-Finally, enjoy the following activities and videos about energy!