Question

TU
(iii) Heat energy : : Some chemical
reactions take place only in the presence of heat.​

Answer 1

Exothermic reactions release heat and light into their surroundings. For example, combustion reactions are usually exothermic. In exothermic reactions, the products have less enthalpy than the reactants, and as a result, an exothermic reaction is said to have a negative enthalpy of reaction