7. Chemical change is always associated with exchange of energy.
1. Chemical reaction or changes may take place spontaneously by bringing reactants in contact. This is usually accompanied by release of heat.
2. During a chemical reaction, the bonds between the atoms of the reactants break. This is made possible by bringing reactants in contact and then by supplying energy like heat, electricity or light. As a result, products are formed.
Thus, a chemical reaction is always associated with an exchange of energy.