What is energy

Energy is the ability to do work. It exists in all things and cannot be created or destroyed, but it can be changed from one form to another.

Energy helps plants to grow, cooks our food, powers our cars and appliances and helps us move. The machines and appliances operating all around you all use some form of energy. It is hard to imagine our life without them!

There are two types of energy – potential energy and kinetic energy.

Forms of potential energy

Energy that is stored and waiting to be released is called potential energy. Below are some examples.

  • Chemical - food stored as fat in the body or power in a battery.
  • Nuclear - the stored energy in an atom.
  • Biomass - energy stored in a piece of firewood that will be released as chemical and heat energy when the wood is burnt.

Forms of kinetic energy

The energy of a moving object is called kinetic energy. Below are some examples.

  • Mechanical - the energy of one object or substance moving another object or substance like wind turbines.
  • Thermal - energy associated with heat, like a hot frypan.
  • Sound - the energy of compression waves, like the banging sound of a door slamming shut.
  • Electrical - the energy of moving charged atomic particles like batteries in a torch.
  • Radiant - the energy of electromagnetic waves, like the light and heat from the sun.
  • Light - light from a source such as a flame or bulb.

Where does energy come from?

Sun imageThe sun is the main source of energy on earth.

Throughout human history the sun has risen every day and filled the earth with light and warmth. Scientists expect the sun to continue shining for billions of years.

As this is such a long time, we can describe the sun as a renewable form of energy.

The sun's energy is needed for plants to make their own food using photosynthesis.

Plants are an important part of the food chain supplying food and energy to other living things. Plants also provide energy in the form of fuel. This may be firewood (biomass) or fossil fuel.

Fossil fuels are made from the remains of ancient plants and animals, buried deep inside the Earth for millions of years. Over a long, long time, heat and pressure has turned these remains into the fossil fuels that we call coal, oil and natural gas.

Fossil fuels are not in endless supply and nature does not replace them as fast as humans now use them. For instance, it takes 400 years to create the amount of coal the world now uses in just one year.

Because this energy takes such a long time to be replaced, we describe this type of energy as non-renewable.

How is energy used?

TabletEnergy is used to do all kinds of work, from moving around, to growing food, to having fun.

Humans have invented many ways to save their own energy and improve their life by using energy in the world around them to do work.

For example, horses were used to enable people to travel further and faster. Tools like bows and spears were developed to help hunt for food more effectively. Over the last 300 years the Industrial Revolution has changed the way humans work and live.

Now we make machines, vehicles and electronic devices to do our work for us while we sit back and think of even more ways to make our lives easier!

Energy in our homes and communities

Washing machinesToday our lives are filled with machines that save us time and effort.

Machines wash our clothes, heat our water, carry heavy things, cook cakes, brush our teeth, heat and cool our homes and even change television channels. We use calculators and computers to save us having to work things out in our heads or on paper.

All of these machines require energy to work. The main sources we use to supply this energy are electricity, natural gas and petrol, derived from oil.

Family in carOur homes require a constant supply of electricity and natural gas. If this supply stops, like in a blackout, many things in and around our homes stop working too.

When we leave our homes to go to school, work or the shops, many of us use a car or bus. Vehicles also require energy to run. We have to fill their tanks with petrol or a form of gas called LPG (liquid petroleum gas).