Chemical energy The energy that keeps atoms bonded to each other in molecules. We make use of chemical energy in fuels. As the fuel burns, the bonds between atoms are broken, which releases energy.

Energy is the ability to make things happen, cause change and carry out work. Energy is all around us, in many different forms, including heat, light, sound, chemical, kinetic, electrical energy and mass. Energy can change from one form to another, or be stored waiting to be used—it is never lost or gained. For example, different energies are converted into electrical energy, which is useful in our modern world. This process is called generating electricity. Without energy, our world would be completely dark and silent.

Fossil fuel A fuel formed from the remains of living things that died millions of years ago. Coal, oil and natural gas are all types of fossil fuel.

Fuel Any source of energy.

Geothermal energy Energy that comes from heat deep inside the Earth. This energy will last for millions of years.

Hydro-electric energy Energy that comes from the kinetic and potential energy of moving water. Hydro-electric power stations control the rush of water through a dam. The movement of the water is used to generate electricity.

Joule The unit used to measure energy. One joule (J) is the energy exerted when a force of one newton moves an object a distance of one metre. A megajoule (MJ) is equal to one million joules.

Kinetic energy The energy that an object has because of its movement. For example, a ball rolling down a hill has kinetic energy. The faster it rolls, the more kinetic energy it has.

Non-renewable energy Energy sources that will eventually run out and cannot be replaced for hundreds of millions of years. Oil and coal are both examples of non-renewable energy sources.

Nuclear energy The energy within an atom, due to the strong force that holds together the protons and neutrons in its nucleus. There are two ways of releasing nuclear energy. These are: nuclear fission and nuclear fusion. They are both forms of nuclear reaction.

Nuclear fission The process of splitting open the nucleus of an atom by blasting it with a high-speed neutron. This can release a huge amount of nuclear energy.

Nuclear fusion The process of fusing together the nuclei of two atoms. This can release an enormous amount of nuclear energy.

Potential energy Energy that is stored. For example, a boulder on a hillside has potential energy. As the boulder starts to roll under the force of gravity, its potential energy changes into kinetic energy. Chemical energy is another type of stored energy.

Power The rate, or speed, at which energy is converted or work is done. Power is measured in watts.

Renewable energy Energy sources that will not run out because they are constantly replenishing themselves. Renewable energy comes from natural sources, such as sunlight, waves, tides, wind and geothermal heat.

Solar energy The heat, light and other energy that is given off by the Sun. A solar cell is a device that converts some kinds of solar energy into electrical energy when the cell is exposed to sunlight.

Watt The unit used to measure power—the speed at which energy is converted. One watt (W) of power is one joule (J) of energy per second.

Work The energy transferred when a force moves an object over a distance. For example, you have to work to lift a box. You must exert a force on the box to overcome the Earth’s gravitational pull. In order to do this you must first have energy, which you obtain in the form of chemical energy from your food.

Consultant: Mike Goldsmith