```
A + B + heat → C + D
```
In this equation, A and B are the reactants, C and D are the products, and heat is the required energy input. The heat is represented by the symbol "ΔH", which stands for "enthalpy change". The enthalpy change is a measure of the amount of heat that is required for the reaction to take place.
The enthalpy change for an endothermic reaction is always positive. This means that the products of the reaction have more energy than the reactants. The heat that is required for the reaction is used to break the bonds in the reactants and to form the bonds in the products.
Endothermic reactions are common in everyday life. Some examples of endothermic reactions include:
* Dissolving salt in water
* Melting ice
* Boiling water
* Cooking food
* Burning fuel
In each of these examples, heat is required for the reaction to take place. The heat is used to break the bonds in the reactants and to form the bonds in the products.
