Question

Does all chemical reactions require heat?

Answer 1

Hey there !

There is something known as threshold energy , which is the energy at which reactant molecules react to produce products and the difference between this normal energy and threshold energy is activation energy which is required for the reactant molecules to yield products.

This is explained in detail in collision theory by Max Trautz(not sure about the spelling)

So even for an exothermic reaction this activation energy is required to yield products. It becomes an exothermic reaction because after the activation energy is supplied the reactant release a large amount of energy while they convert into products. It can be simply explained by saying a positive quantity(activation energy)+ a larger negative quantity in magnitude(energy released by reactants)= a smaller negative quantity (net energy released) hence making it an exothermic reaction

Hope it helps you !

Answer 2

there are many exothermic reaction that requires heat but not all......all reactions say for example combustion reaction requires a certain amount of heat supplied to cross the energy barrier called threshold energy or activation energy.