What is the main difference between an exothermic and an endothermic reaction?

The main difference between exothermic and endothermic reactions lies in how they exchange heat with their surroundings. In an exothermic reaction, energy is released to the surroundings, typically in the form of heat. This results in an increase in the temperature of the surroundings and is commonly observed in processes like combustion and respiration.

In contrast, endothermic reactions absorb energy from the surroundings, which can lead to a decrease in temperature in the environment around the reaction. These types of reactions are often seen in processes like photosynthesis and dissolving certain salts in water.

By recognizing that exothermic reactions release heat while endothermic reactions absorb heat, you can understand how these reactions impact energy flow in chemical processes and the surrounding environment, which is essential knowledge in chemistry.