Describe the differences between exothermic and endothermic reactions.

Exothermic reactions release energy, while endothermic reactions absorb energy.

Exothermic reactions are those that release energy in the form of heat, light, or sound. This means that the products of the reaction have less energy than the reactants, and the excess energy is released into the surroundings. Examples of exothermic reactions include combustion, where a fuel reacts with oxygen to release heat and light, and neutralisation, where an acid and a base react to form water and a salt, releasing heat in the process.

Endothermic reactions, on the other hand, absorb energy from the surroundings. This means that the products of the reaction have more energy than the reactants, and the extra energy comes from the surroundings. Examples of endothermic reactions include photosynthesis, where plants absorb energy from sunlight to convert carbon dioxide and water into glucose and oxygen, and melting ice, where energy is absorbed to break the bonds between the water molecules.

The energy changes in exothermic and endothermic reactions can be measured using calorimetry, which involves measuring the temperature change of the surroundings. Exothermic reactions cause the temperature to increase, while endothermic reactions cause the temperature to decrease. Understanding the differences between exothermic and endothermic reactions is important in many areas of biology, including metabolism, respiration, and thermoregulation.