Exothermic and endothermic reactions

• Exothermic reactions transfer energy to the surroundings and the temperature of the surroundings increases.
• Endothermic reactions take in energy and the temperature of the surroundings decreases.
• Energy is conserved in chemical reactions, so the total amount of energy before and after a reaction is the same.
• The capacity of a system to do work or the quantity required for mechanical work to take place is measured in joules (J).
• In the universe, the total amount of energy at the end of a reaction is the same as it was before the reaction.
• When a chemical reaction happens, energy is transferred to or from the surroundings.
• Endothermic reactions require energy to proceed and the temperature of the surroundings decreases.
• Examples of endothermic reactions include thermal decomposition and the reaction of citric acid and sodium hydrogencarbonate.
• Endothermic reactions are used in everyday life, for example, in instant ice packs which can be used to treat sports injuries.
• Exothermic reactions release energy and the temperature of the surroundings rises.
• Examples of exothermic reactions include the reaction of sodium carbonate and ethanoic acid and the reaction of dilute sodium hydroxide and hydrochloric acid.
• Endothermic reactions involve energy entering the system, while exothermic reactions involve energy exiting the system.
• When energy is transferred to the surroundings, this is called an exothermic reaction, and the temperature of the surroundings increases.
• Examples of exothermic reactions include: combustion, reactions, many oxidation reactions, and most neutralisation reactions.
• Everyday uses of exothermic reactions include self-heating cans and hand warmers.
• When energy is taken in from the surroundings, this is called an endothermic reaction, and the temperature of the surroundings decreases.
• Examples of endothermic reactions include: the process of cooling, reactions, and most reactions involving the formation of ice.
• Everyday uses of endothermic reactions include freezing food and making ice cubes.