Question

Is melting exothermic or endothermic?

Answer 1

For a substance to melt, thermal energy is required, and this process cools down the surroundings.

Complete step-by-step answer: In order to answer our question, we need to learn about exothermic and endothermic reactions. It is to be known that for any reaction to take place, a specific amount of energy is required, and this energy is called the activation energy. Now, energy can neither be created nor destroyed, so when energy is given to a reaction to take place, so, energy will either be liberated from the reaction, or energy will be gained.
So, two cases arise here. Suppose in the first case, the reaction takes place and gives out energy in the form of thermal energy, or heat. So, we call this type of reaction an exothermic reaction. In an exothermic reaction, heat escapes from the reaction, which makes the reactants and products cooler, and the surroundings become hot.
In the other case, we can think of a reaction, where energy is taken in. This type of reaction is called endothermic reaction. In an endothermic reaction, heat is taken in from the surroundings, which makes the reactants and products warm, and the surroundings cool.
In case of melting, energy is required in the form of heat. For example, when ice melts, heat is taken from the surroundings, and due to this, ice melts and surroundings become cooler. Hence, melting is an example of an endothermic process.

Note: It is to be noted that in exothermic reactions, energy can be liberated in the form of heat, light and sound. In exothermic reactions, $\Delta H<0$ and in case of endothermic reactions,$\Delta H>0$.