The heat of reaction is the amount of heat absorbed or released during a chemical reaction. It tells us whether a reaction releases energy (exothermic) or requires energy (endothermic).
Key points:
- Exothermic reaction – Heat is released into the surroundings, so the temperature of the surroundings increases. Example: burning wood or combustion of fuels.
- Endothermic reaction – Heat is absorbed from the surroundings, so the temperature of the surroundings decreases. Example: photosynthesis or dissolving ammonium chloride in water.
- The heat of reaction depends on the reactants, products, and conditions of the reaction.
In simple terms, it’s a measure of the energy change during a chemical reaction, showing whether the reaction gives out heat or takes in heat.