# Energy level diagrams

are used to model changes during reactions. They show the relative energy levels of the and .

## Exothermic reaction

The energy level decreases in an reaction. This is because energy is given out to the surroundings.

A downwards arrow shows that energy is given out

## Endothermic reaction

The energy level increases in an reaction. This is because energy is taken in from the surroundings.

An upwards arrow shows that energy is taken in
Question

Look at the energy level diagrams below. Which reaction is more exothermic?

The reaction shown by the second diagram is more exothermic. There is a greater difference in energy between the reactants and products. The green arrow is longer.