During chemical reactions energy is always transferred to or from the surroundings.
The two types of reactions that can occur are called Endothermic and Exothermic.
An exothermic reaction is the one that transfers energy to the surroundings, which is usually done in the form of heat. You can recognize this reaction from the rise in temperature.
An example of an exothermic reaction is a neutralisation reaction, so when a acid and a alkali react together.
Another example of an exothermic reaction could be combustion (burning fuels) as it gives out a lot of heat.
As well as that, oxidation reactions are also exothermic -because they produce heat (transfers heat to surroundings).
We use Exothermic reactions on a daily basis, for example:
- hand warmers
- self heating cans ( for hot chocolate and coffee )