Know that in for endothermic reactions H products > H reactants, ∆ H> 0 and reaction absorbs
energy

In chemical reactions, an endothermic reaction is one that absorbs energy from the surroundings. It is characterized by the fact that the enthalpy (H) of the products is greater than the enthalpy of the reactants. This change in enthalpy (∆H) is positive, indicating that energy is absorbed during the reaction.

To understand endothermic reactions, let's consider an everyday example: the process of cooking pasta. When you boil water and add pasta to it, the reaction between the pasta and the hot water is endothermic. The energy from the heat source is absorbed by the pasta, causing it to cook and increase in temperature.

In an endothermic reaction, the potential energy of the products is higher than that of the reactants. This means that the reactants have a lower energy level compared to the products. As the reaction progresses, energy is absorbed from the surroundings, leading to an increase in potential energy.

On a potential energy diagram for an endothermic reaction, the reactants are represented at a lower energy level compared to the products. The curve starts at a lower point (representing the energy of the reactants) and gradually increases (representing the increase 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 absorbed from the surroundings.

The positive value of ∆H indicates that the reaction absorbs energy. This energy can be in the form of heat, light, or any other form of energy. In the case of the cooking pasta example, the absorbed energy is in the form of heat from the boiling water.

Endothermic reactions are essential in various processes. For instance, in photosynthesis, plants absorb energy from sunlight to convert carbon dioxide and water into glucose and oxygen. This process requires energy input to drive the reaction.

Another example is the process of evaporation. When a liquid evaporates, it absorbs energy from the surroundings, causing a cooling effect. This is because the liquid particles need to gain energy to break the intermolecular forces and transform into a gas state.

Endothermic reactions are also prevalent in chemical reactions used for cooling, such as instant cold packs or ice packs. These packs contain chemicals that undergo an endothermic reaction when activated, absorbing heat from the surroundings and providing a cooling sensation.

In summary, endothermic reactions are characterized by the absorption of energy from the surroundings. The enthalpy of the products is greater than that of the reactants, resulting in a positive change in enthalpy (∆H). On a potential energy diagram, the potential energy increases from the reactants to the products, indicating the energy absorbed during the reaction. Understanding endothermic reactions helps us comprehend processes that require energy input and have a cooling effect, such as cooking, photosynthesis, evaporation, and cooling packs.