What are common examples of exothermic reactions?

Common examples of exothermic reactions include combustion, neutralisation reactions, and the reaction between water and calcium oxide.

Combustion is a well-known exothermic reaction. It involves the reaction of a substance with oxygen, producing heat and light energy. A common example is the burning of wood or coal in a fireplace. The heat produced in this reaction is what makes the fire hot and the light energy is what makes the fire glow. Another example is the combustion of petrol in a car engine, which provides the energy to move the car.

Neutralisation reactions are another type of exothermic reaction. These occur when an acid reacts with a base, producing water and a salt, and releasing heat. For example, when hydrochloric acid reacts with sodium hydroxide, the result is sodium chloride (table salt) and water. The heat produced in this reaction can be felt if you touch the container where the reaction is happening.

The reaction between water and calcium oxide, also known as quicklime, is a further example of an exothermic reaction. When water is added to calcium oxide, it reacts to form calcium hydroxide, also known as slaked lime, and releases a significant amount of heat. This reaction is used in self-heating cans, such as those used for camping meals.

In all these examples, the reactions are exothermic because they release more energy to the surroundings than they absorb. This is why they result in an increase in temperature. Understanding these reactions is important in many areas of chemistry and everyday life, from understanding how a fire burns to how a car engine works.