Reaction profiles - higher tier
Energy level diagrams
An energy level diagram shows whether a reaction is exothermic or endothermic. It shows the energy in the Substances present at the start of a chemical reaction. and Substances formed in a chemical reaction., and the difference in energy between them.
Exothermic reaction
The energy level decreases in an exothermic reaction, as energy is given out to the surroundings.
Endothermic reaction
The energy level increases in an endothermic reaction, as energy is taken from the surroundings.
Reaction profile
A Chart showing how the energy of reactants and products changes during a reaction. is similar to an energy level diagram, but it includes the The activation energy is the minimum energy required for a reaction to occur. 鈥 the minimum energy that particles need when they collide for a reaction to occur. The activation energy is a hump in the line, which:
- starts to rise from the same energy as the reactants
- is equal to the difference in energy between the top of the hump and the reactants.
The overall change in energy is the difference between the energy of the reactants and products.