1. What is energy?
2. The properties of energy
3. Forms of energy
4. Energy transforms
5. Sources of energy
6. Responsible use of energy
What is energy?
Look around you, the Sun produces heat and light, cars use energy to move, computers use energy to work, plants use energy to produce food, birds use energy to fly, your body uses energy to grow, keep warm or play…
The energy contained in matter is invisible, but light, movement, wind, and waves are some of the ways energy manifests.
So, What is energy?
Look at the photos and find more examples of energy.
Energy is the ability to do work, to cause changes, or to produce motion, heat or light.
Energy has some important properties that help us to use it efficiently.
The properties of energy
The universe contains a constant, finite amount of energy. This is called the law of conservation of energy.
When you roll a marble on the ground, it slows down and stops because of friction. But this does not mean that the energy was destroyed. The energy was converted into heat and transmitted to the ground and the air.
ENERGY CANNOT BE
CREATED OR DESTROYED
Energy can be transferred from one object to another. There is no transformation of energy. The heat from a cooker is transferred to the pan. On a bicycle, the movement of the pedals is transmitted to the wheels. When one marble hits another, it transmits a certain amount of motion…
Energy can change forms. Energy often transforms when it is transmitted. For example, the energy contained in wood transforms into heat and light when the wood is burned. The energy from the Sun is converted into food (chemical energy) by plants thanks to a process called photosynthesis.
TRANSFORMATION
OF ENERGY
TRANSFER
OF ENERGY
Each domino transmits its energy to the other. They have to be in contact.
The windmills transform the energy from the wind into electrical energy.
Energy can be transported. For example, the electrical energy “produced” in a power plant that uses water, wind, coal or natural gas is transported through distribution lines to your home.
Energy can be stored in different forms. Chemical energy is stored in batteries, fuel or food. For example torches transform the chemical energy stored in batteries into light energy; the body digests and transform chemical energy stored in food into growth, heat or movement; cars transform the chemical energy stored in fuel into movement.
TRANSPORT
OF ENERGY
STORAGE
OF ENERGY
Car battery
Forms of energy
Energy appears in many forms. The main ones are: mechanical, chemical, electrical, light (radiant), thermal (heat) and nuclear.
Mechanical Energy
Mechanical Energy is the energy that produces or can produce motion. Mechanical energy includes both kinetic energy and potential energy.
Kinetic Energy
Potential Energy
Kinetic energy is the energy of motion. A spinner, a falling object, the wind or a river have kinetic energy.
As the ball rolls down the hill, kinetic energy increases and potential energy decreases.
Potential energy is the energy stored by an object as a result of its position. A ball at the top of a hill has potential energy.
Height and the pull of gravity give this ball potential energy.
Mechanical energy = Kinetic energy + Potential energy
Electrical Energy
Chemical Energy
It is the energy stored in some substances and released during chemical reactions. For example chemical energy is stored in fuel, food or batteries.
1. The Sun produces light energy.
2. Plants turn the light into chemical energy.
3. Plants are fossilized and compressed into fossil fuels like coal and oil. These fossil fuels preserve the chemical energy.
4. Fossil fuels are burned in power plants to produce electricity for our homes and schools.
It is a form of energy produced when electrons move from one place to another. Lots of machines use electrical energy.
Lightning are natural sources of electrical energy.
Light Energy
Thermal Energy
It is the energy produced when the molecules in a substance vibrate producing heat. When an object absorbs thermal energy, it heats up. When the object releases thermal energy, it cools down.
It is a form of energy that travels in waves and can move through empty spaces where there is no air. The Sun is a natural
source of light. Torches
cameras or computers
also produce light that
enables us to see.
Volcanoes are natural sources of thermal energy.
Thermal energy travels by:
Street lights and candles produce light energy too.
Mobile, camera or computer screens produce light energy.
Nuclear Energy
It is the energy stored in the nucleus of an atom. Nuclear energy is released by breaking down radioactive materials such as uranium or radium.
Nuclear energy is produced in nuclear power stations.
The sun and other stars produce their energy through nuclear reactions.
Is sound a form of energy?
Energy transforms
Energy cannot be created or destroyed. It transforms continuously from one form of energy to a different one. Some common examples are:
The forklift loses chemical energy, by consuming gasoline and it gains kinetic energy. The boxes also gain potential energy.
1. Stored water has potential energy.
3. Generator transforms kinetic energy into electrical energy
4. High voltage lines transport electrical energy.
2. Water flows through turbine.
It loses potential energy and gains kinetic one.
The battery loses chemical energy and the light bulb emits light and heat energy.
Most means of transport transform chemical energy from the fuel into mechanical (kinetic and potential) and thermal energy.
The wind transfers kinetic energy to the windmill. There is no transformation of energy.
The chemical energy stored in food is measured in calories. Our body transforms it into kinetic and thermal energy.
Solar panels transform the light energy from the sun into heat and electrical energy. The electrical energy can be stored in batteries or transported to our homes and businesses.
Can you guess what transformation occurs in this old windmill?
And at home we find lots of examples of transformation of electrical energy into:
Sources of energy
We cannot create energy. We get energy from natural sources. They can be renewable, like the Sun or wind; or non-renewable, like petroleum or coal.
Renewable Sources
Renewable energy sources replace energy rapidly by a natural process. Renewable resources include: hydroelectric energy, wind energy, solar energy, geothermal energy and biofuels.
Wind Energy
Hydroelectric Energy
Reservoir
Dam
Turbines
We get hydroelectric energy from water that is moving or falling. The dam holds the water and collects it in the reservoir. When the water falls, its kinetic energy moves the turbines that transform the kinetic energy into electrical one.
We get wind energy from the movement of the air. The kinetic energy in the air moves the turbines in the mills. The turbines transform the kinetic energy into electrical one.
Turbines
Renewable Sources
Solar Energy
Geothermal Energy
We get solar energy from the Sun. The solar panels transform the light energy from the Sun into electrical energy. There are also panels that produce thermal energy.
Some solar panels produce electricity.
Other solar panels are used to heat water.
We get geothermal energy from the inner heat of the Earth. In some areas groundwater can be at high temperatures. We can use the thermal energy of groundwater to produce electricity, to heat buildings or we can use the hot water directly.
Renewable Sources
Biofuels
We get biofuels from plants and animals. They can be solid (biomass), liquid (bioliquids) of gas (biogases). Biofuels are burned in power stations to produce electricity or they are burned in boilers to heat homes (pellet). Biofuels are renewable sources of energy, but they are not clean.
Hydroelectric Energy
Wind Energy
Solar Energy
Geothermal Energy
Biofuels
Let’s
revise
Non-renewable Sources
Non-renewable sources of energy don’t replace energy rapidly. They are limited. Non-renewable sources of energy include: petroleum, coal, natural gas and uranium.
Coal
Petroleum is a black liquid rock. It was formed underground from decayed animals and plants that lived millions of years ago. The petroleum is transformed into fuel oil, diesel oil and petrol that we use for heating or running vehicles.
Petroleum is also used to produce electricity in power stations.
Coal is a black rock. It was also formed from decayed plants that lived million of years ago. Coal is used as fuel in some industries and to produce electricity in power stations.
Petroleum
Non- renewable Sources
Natural Gas
Natural gas is a mixture of gases formed underground from decayed animals and plants that lived millions of years ago. Natural gas is used as fuel in many industries and to produce electricity in power stations. It is also used in homes for cooking or heating.
Uranium is a radioactive metal found in rocks. It is used in nuclear power stations to produce electricity.
Natural Gas
Seal
Gas reservoir
(sandstone)
Gas source rock
(coalbed methane)
Responsible use of energy
Energy is essential for life. However, if we use a lot of non-renewable energy we won’t have enough energy in the future. We can save energy or use renewable energy instead.
Problems of non-renewable energy
acidic gases released into the atmosphere
gases carried upwards by the wind
gases combine with water droplets to form acids
acid rain
acid rain destroys plants, pollutes water sources and soil and erodes buildings.
transport, at home, or in power
stations to produce electricity. It
causes pollution (carbon dioxide,
nitrogen oxide or sulphur dioxide).
These gases cause pollution,
global warming and acid rain.
They also cause illnesses.
Solutions
1. Reduce. Buy products that have little packaging.
Use reusable bags.
To help the environment, we have to save as much energy as possible. And we have to use as much renewable and clean energy as possible. The three Rs help us to use fewer resources and save energy.
2. Reuse. Use plastic, metal and glass containers again and again. Be creative.
3. Recycle. When you cannot reuse it, put it in the correct bin.