Physics Is Life
Me

Unit 4, lesson 18. About 12 minutes.

What is energy?

What do a running child, a light bulb and the Sun have in common?

Play

Getting the experiment ready…

Explain

Energy makes things happen.

Food, sunshine and batteries all have energy.

Energy is what makes things happen. You can't see it, but it is in everything that moves, glows or gets warm.

Energy comes in many forms: movement, height, heat, light, sound, chemical and electrical.

Energy can change from one form to another. Pick an example to follow it.

Energy is a quantity that is transferred between stores whenever something happens. Its SI unit is the joule (J).

Common stores are kinetic, gravitational, elastic, chemical, thermal and nuclear. Energy transfers between them through forces, heating, electric currents and waves.

Example: a torch transfers chemical energy to electrical energy, then to light and thermal energy.

  1. Energy is stored
  2. It moves or changes form
  3. Things happen
Want the full story?

Scientists find it hard to say exactly what energy is. It is best seen as a number that stays the same, however things change. Calling these "forms" of energy is a helpful simplification. Most useful energy ends up spreading out as heat.

Try it at home

Ask a grown-up to help

You need your hands, a rubber band.

You need: your hands, a rubber band.

Rub your hands fast. Feel them get warm!

  1. Rub your hands together quickly for 10 seconds.
  2. Feel how warm they get.
  3. Stretch a rubber band gently a few times, and feel it with your fingers.

What's happening: movement energy from your muscles turned into heat. Stretching the band also warms it a little.

Physics is life

Your body

Food gives your body energy.

Your body uses chemical energy from food to move, think and stay warm.

Daily life

Batteries and plugs give energy.

Lights, screens and heaters all change electrical energy into other forms.

Nature

Plants catch energy from the Sun.

Plants store energy from sunlight in sugars, which feed nearly all life on Earth.

Space

The Sun gives out huge energy.

Almost all of the energy that living things use began as sunlight.

Quick check

Question 1 of 3

Which of these is a form of energy?

Words to know

Energy: What makes things able to happen. It is measured in joules.

Energy
What makes things able to happen. It is measured in joules.
Joule (J)
The unit of energy. It takes about 1 joule to lift an apple 1 metre.
Kinetic energy
The energy something has because it is moving.

Next up

Movement energy: kinetic energy