Reaction profile diagrams: Energy Changes: Chemistry: GCSE (9:1)

Requirements for a reaction to take place

Particles must collide, with sufficient energy

Activation energy

Minimum amount of energy required to start a chemical reaction

Reaction profile diagram

A graph which shows the change in energy of a chemical reaction

Products

The new substances formed by a chemical change

Reactants

The starting material in a chemical reaction

Reaction profile - exothermic

Reactants are at higher energy than products

Reaction profile - endothermic

Products are at a higher energy than the reactants

Reaction profile - activation energy

An arrow starting at reactants and going to the highest

Reaction profile - overall energy changes

An arrow starting at reactions going to products

Bond breaking

Endothermic

Bond making

Exothermic

Bond energy

Average amount of energy that will break/make a bond between two atoms

Formula for overall energy change

Energy required to break bonds - energy required to break bonds

Reason for exothermic reactions

More energy is given out when new bonds are formed than is taken in to break bonds

Reason for endothermic reactions

More energy is required to break bonds than is given out when new bonds formed

Catalyst

A substance that speeds up the rate of a chemical reaction without being used up

How catalysts work

They provide an alternate reaction pathway with lower activation energy