Any property that describes how a substance reacts with another substance when forming a new substance is the Property of Reactivity .
Explanation:
The ability of substance to readily react with other substance to produce new product is called as reactivity.
It describes about different methods used by the reactants to form new product.
Sometimes one single reactant gives rise to two different products as in splitting of water during which the following reaction takes place:
H_2 O →2H_2 + O
On contrary, two substance combines together to give rise to one single product as:
2 Mg + O_2 →2MgO