You might think that the way cars work has nothing in common with how people work, but you would be wrong.

When it comes to the way cars and bodies use energy, they do just the same job.

Can you spot the Difference?

A body gets energy from food molecules. These are made of long chains of carbon atoms joined together by plants. The sun’s energy became trapped in the molecules as the plants constructed them.	A car gets energy from fuel molecules. These are made of long chains of carbon atoms joined together by plants. The sun’s energy became trapped in the molecules as the plants constructed them.
Inside a body, food molecules react with oxygen sucked in from the air. The reaction breaks down the bonds between carbon atoms and rearranges the atoms into new combinations. This frees the trapped energy. Oxygen and carbon atoms join to make carbon dioxide, which the lungs must breathe out.	Inside a car, fuel molecules react with oxygen sucked in from the air. The reaction breaks down the bonds between carbon atoms and rearranges the atoms into new combinations. This frees the trapped energy. Oxygen and carbon atoms join to make carbon dioxide, which the exhaust must breathe out.
The chemical energy freed from food molecules is converted into new forms of energy: heat and movement.	The chemical energy freed from fuel molecules is converted into new forms of energy: heat and movement.

A Basic Equation

Cars and bodies are powered by the same basic equation:

FUEL + OXYGEN > ENERGY + CO2 + WATER

The energy that powers our bodies and our cars comes from the sun as light energy. Plants convert light into chemical energy, which then becomes trapped when dead plants are turned into food or petrol.

The chemical energy is then changed into kinetic (movement) energy by a car’s engine or a human body.

Energy never really gets ‘used up’, it just keeps getting changed from one form to another.

LIGHT ENERGY > CHEMICAL ENERGY > KINETIC ENERGY