Exothermic reactions are chemical reactions that release energy. The energy release usually in the form of heat. While endothermic reactions are chemical reactions that absorb energy.
Any elements or compounds in existence within a specific system needs the energy to maintain its state. If a compound wants to change to another product they need to release or absorb heat to meet the requirement of the new products.
Exothermic reaction
If the level of energy of the product is less than the original compound, the excess energy will be released in the form of heat. For example, adding water to solid calcium oxide will cause the mixture to heat up. This is because calcium dihydroxide formed has lower energy than water and calcium hydroxide combined. Hence, the excess energy released in the form of heat and this reaction is known as an exothermic reaction.
Endothermic reaction
If the level of energy of the product is higher than the original compound, it needs to absorb energy in order to change. Without added energy, the compound cannot change its state to the product. To get the necessary energy, the system may adsorb energy from it surrounding and causing the temperature to drop at the nearby of the system.
For example, is a reaction between barium hydroxide and ammonium chloride. The product of the reaction is barium dichloride, ammonia, and water. The total energy of the products combined is larger than the total energy of the original compounds. Thus, the temperature close to the system where the reaction took place is cooled down. Since the energy nearby is adsorbed during the reaction. such a reaction is known as an endothermic reaction.
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