Chemical reactivity is the ability of a chemical substance to undergo a chemical reaction. It is a measure of how likely a substance is to react with another substance. Chemical reactivity is not a characteristic property because it depends on the conditions of the reaction, such as the temperature, pressure, and concentration of the reactants. For example, sodium is a highly reactive metal, but it will not react with water at room temperature. However, if the temperature is increased, sodium will react with water to produce sodium hydroxide and hydrogen gas.