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

Combustion is one of the most recognized exothermic reactions. It occurs when a substance reacts with oxygen, resulting in the release of heat and light energy. A typical example is the burning of wood or coal in a fireplace. The heat generated during this reaction is what makes the fire hot, while the light energy emitted creates the fire’s glow. Another illustration of combustion is the burning of petrol in a car engine, which provides the necessary energy to propel the vehicle.

Neutralization reactions represent another category of exothermic reactions. These occur when an acid reacts with a base, producing water and a salt while releasing heat. For instance, when hydrochloric acid ($\text{HCl}$) reacts with sodium hydroxide ($\text{NaOH}$), the products are sodium chloride ($\text{NaCl}$), commonly known as table salt, and water ($\text{H}_2\text{O}$). The heat generated by this reaction can often be felt if you touch the container in which the reaction is taking place.

Another notable exothermic reaction is the interaction between water and calcium oxide, commonly referred to as quicklime. When water ($\text{H}_2\text{O}$) is added to calcium oxide ($\text{CaO}$), it reacts to form calcium hydroxide ($\text{Ca(OH)}_2$), also known as slaked lime, while releasing a substantial amount of heat. This reaction is utilized in self-heating cans, such as those designed for camping meals.

In all these instances, the reactions are classified as exothermic because they release more energy to the surroundings than they consume. This energy release accounts for the increase in temperature observed during these processes. Understanding these reactions is crucial in various fields of chemistry and everyday applications, from comprehending how a fire burns to understanding the operation of a car engine.

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