 What's the difference between an endothermic reaction and an exothermic reaction? This is an exothermic reaction. It releases energy into its surroundings in the form of heat. As you can see, the temperature of the mixture is increasing. This is an endothermic reaction. For it to occur, it needs energy in the form of heat from its surroundings. The temperature is decreasing because the heat from the mixture is being used by the reaction. You can do both of these experiments at home by checking out the instructions below or by clicking on the information icon right up there. Just remember to wear some eye protection, some gloves, something to cover your clothes. That's it! Have fun!