This is an endothermic reaction Energy has been taken from the surroundings This is the energy released when the bonds form This is the activation energy. The energy supplied to break the bonds Products Energy in the molecules bonds The products are at a higher energy level, so energy has had to be taken in from the surroundings. Reactants

Energy in the molecule’s bonds This is the activation energy. The energy supplied to break the bonds. Energy in the molecule’s bonds Reactants This is the energy released when the bonds form. Products The products are at a lower energy level, so energy has had to be released to the surroundings. This is an exothermic reaction. Energy has been released to the surroundings

Energy in the molecule’s bonds A catalyst lowers the activation energy and thus speeds up chemical reactions Energy in the molecule’s bonds The overall energy changes however remain the same Remember the catalyst does not get used up in the reaction so is use over and over again

Therefor this is an endothermic reaction 2H2O  2H2 + O2 Therefor this is an endothermic reaction y-This is the energy released when the bonds in the hydrogen and oxygen form Energy in the molecule’s bonds x-This is the activation energy. The energy supplied to break the bonds in the water Products z-The products are at a higher energy level, so energy has had to be taken in from the surroundings. 1856-1370=486kJ is absorbed from the surroundings Reactants