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

The primary difference between an endothermic and an exothermic reaction lies in the direction of energy flow. In an endothermic reaction, energy is absorbed from the surroundings, which often results in a temperature drop in the environment as the reaction requires energy input to proceed. This is typically seen in processes like photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen.

Conversely, an exothermic reaction releases energy to the surroundings, often in the form of heat, light, or sound. This leads to an increase in the temperature of the environment. Common examples include combustion reactions, such as burning fossil fuels, where energy is released as the chemical bonds are broken and formed.

Overall, understanding the distinction between these two types of reactions is crucial in fields like chemistry and thermodynamics, as it impacts the behavior of substances and the energy changes associated with chemical processes.