How do endothermic reactions differ from exothermic reactions?

Endothermic reactions absorb heat from the surroundings, while exothermic reactions release heat into the surroundings.

In more detail, endothermic and exothermic reactions are two types of chemical reactions that differ based on the flow of heat. In an endothermic reaction, the system absorbs heat from its surroundings. This means that the reaction cannot occur without an external source of heat. The term 'endothermic' comes from the Greek words 'endo', meaning inside, and 'therm', meaning heat. This type of reaction often feels cold to the touch because it is taking in heat from its surroundings. Examples of endothermic reactions include photosynthesis in plants and the process of cooking an egg.

On the other hand, an exothermic reaction is one where heat is released into the surroundings. The system loses heat because the energy required to break the bonds in the reactants is less than the energy released when new bonds are formed in the products. The term 'exothermic' comes from the Greek words 'exo', meaning outside, and 'therm', meaning heat. This type of reaction often feels hot to the touch because it is releasing heat. Examples of exothermic reactions include combustion reactions, such as a burning candle or a firework explosion.

In terms of energy diagrams, endothermic reactions have a higher energy level for the products than the reactants, indicating that energy has been absorbed. Conversely, exothermic reactions have a lower energy level for the products than the reactants, showing that energy has been released.

Understanding the difference between endothermic and exothermic reactions is crucial in chemistry as it helps predict the energy changes that occur during a reaction. This knowledge can be applied in various fields, from industrial processes to environmental science.