Lesson 9: Endothermic 

and Exothermic Reactions

When a chemical reaction occurs, energy is transferred to or from the surroundings — and there is often a temperature change. For example, when a bonfire burns, it transfers heat energy to the surroundings. Objects near a bonfire become warmer. The temperature rise can be measured with a thermometer. In this lesson, you will learn about endothermic and exothermic reactions.