Exothermic reaction is the reaction in which heat is evolved
i endothermic reaction heat is absorbed.

Exothermic Reactions:
Exothermic reactions are chemical reactions that release energy in the form of heat to the surroundings. In these reactions, the products have a lower energy than the reactants, resulting in the release of energy. Here are some key points to understand about exothermic reactions:

Release of Energy: Exothermic reactions release energy in the form of heat, light, or sound. This energy is often observed as an increase in temperature.

Energy Level: In exothermic reactions, the energy level of the products is lower than that of the reactants. The difference in energy is released as heat.

Examples: Some common examples of exothermic reactions include combustion reactions (burning of fuel), neutralization reactions (acid-base reactions), and oxidation reactions.

Energy Flow: In exothermic reactions, the energy flows from the system (reactants) to the surroundings. This means that the system loses energy, resulting in a decrease in the internal energy of the system.

Sign of ΔH: The enthalpy change (ΔH) for exothermic reactions is negative because the system releases energy.

Endothermic Reactions:
Endothermic reactions are chemical reactions that absorb energy from the surroundings in the form of heat. In these reactions, the products have a higher energy than the reactants, resulting in the absorption of energy. Here are some key points to understand about endothermic reactions:

Absorption of Energy: Endothermic reactions absorb energy from the surroundings in the form of heat. This energy is often observed as a decrease in temperature.

Energy Level: In endothermic reactions, the energy level of the products is higher than that of the reactants. The difference in energy is absorbed from the surroundings.

Examples: Some common examples of endothermic reactions include photosynthesis, evaporation, and the reaction between ammonium nitrate and water.

Energy Flow: In endothermic reactions, the energy flows from the surroundings to the system (reactants). This means that the system gains energy, resulting in an increase in the internal energy of the system.

Sign of ΔH: The enthalpy change (ΔH) for endothermic reactions is positive because the system absorbs energy.

Overall, exothermic reactions release energy to the surroundings, while endothermic reactions absorb energy from the surroundings. The energy changes in these reactions can be measured using the enthalpy change (ΔH), which indicates the overall energy change of the system.