Chemical Reactions: Exothermic vs Endothermic In chemistry, we classify chemical reactions based on the energy changes that occur during the reaction process. T...
In chemistry, we classify chemical reactions based on the energy changes that occur during the reaction process. The two main types are exothermic and endothermic reactions.
Exothermic reactions release energy to the surroundings, often in the form of heat. As reactants form new products, the bonds in the products are stronger and more stable than the reactant bonds, resulting in an overall release of energy.
CH4 + 2O2 → CO2 + 2H2O + Energy
This reaction is exothermic, releasing heat energy that warms the surroundings.
Endothermic reactions absorb energy from the surroundings, often as heat. Breaking the existing bonds in reactants requires an energy input, and the new bonds formed in the products are weaker, resulting in an overall absorption of energy.
CaCO3 → CaO + CO2 + Energy (absorbed)
This reaction is endothermic, requiring heat energy from the surroundings to proceed.
Reaction profiles show the energy changes during a chemical reaction, including the activation energy required to initiate the reaction. Exothermic reactions release energy, while endothermic reactions absorb energy, as shown in their respective profiles.
During chemical reactions, existing bonds in reactants must be broken, requiring an energy input. Subsequently, new bonds form in the products, releasing energy. The overall energy change is the difference between the energy required for bond breaking and the energy released during bond formation.
Chemical cells and fuel cells are devices that generate electricity from chemical reactions. In these systems, exothermic reactions provide the energy needed to drive an electric current, allowing for the conversion of chemical energy into electrical energy.