Know that in for exothermic reactions H products < H reactants, ∆ H< 0 and reaction releases
energy

In chemical reactions, an exothermic reaction is one that releases energy to the surroundings. It is characterized by the fact that the enthalpy (H) of the products is less than the enthalpy of the reactants. This change in enthalpy (∆H) is negative, indicating that energy is released during the reaction.

To understand exothermic reactions, let's consider an everyday example: the combustion of a candle. When you light a candle, the wax reacts with oxygen in the air, and an exothermic reaction occurs. The energy stored in the wax is released as heat and light, producing a flame.

In an exothermic reaction, the potential energy of the products is lower than that of the reactants. This means that the reactants have a higher energy level compared to the products. As the reaction progresses, energy is released to the surroundings, resulting in a decrease in potential energy.

On a potential energy diagram for an exothermic reaction, the reactants are represented at a higher energy level compared to the products. The curve starts at a higher point (representing the energy of the reactants) and gradually decreases (representing the decrease in potential energy) as the reaction proceeds towards the products. The difference in potential energy between the reactants and products is the amount of energy released to the surroundings.

The negative value of ∆H indicates that the reaction releases energy. This energy can be in the form of heat, light, or any other form of energy. In the case of the candle combustion example, the released energy is in the form of heat and light from the burning flame.

Exothermic reactions are crucial in various processes. For instance, the combustion of fuels, such as gasoline in car engines or natural gas in stoves, is exothermic. The energy released during combustion is harnessed to perform useful work, such as powering vehicles or heating homes.

Another example is the process of respiration in living organisms. Through cellular respiration, energy is released from glucose and other molecules, providing the necessary energy for cellular functions and activities.

Exothermic reactions also play a role in many natural phenomena, such as the formation of crystals, the release of energy during chemical reactions in the human body, and the generation of heat and light in firework explosions.

In summary, exothermic reactions are characterized by the release of energy to the surroundings. The enthalpy of the products is less than that of the reactants, resulting in a negative change in enthalpy (∆H). On a potential energy diagram, the potential energy decreases from the reactants to the products, indicating the energy released during the reaction. Understanding exothermic reactions helps us comprehend processes that release energy, such as combustion, respiration, and various natural phenomena.