The BasicsEdit

An exothermic reaction releases energy to the environment.

This means it makes its container's temperature rise.

The vast majority of reactions encountered will be exothermic.


Note: The Activation Energy corresponds to the bond-breaking, the Enthalpy (H) change is the difference between bond-breaking and bond-forming.

Exam HintsEdit

Remember that all reactions start with bond-breaking - this requires energy and so is endothermic.

However, new bonds will form, releasing energy. And bond formation is always exothermic.

So a reaction can only be exothermic if less energy is required to break bonds than is then released when the new bonds are formed.