Which characteristic of a substance is considered a chemical property? is it boiling point or reactivity or density or conductivity

Reactivity is the is an example of chemical property.

Explanation:

Chemical property is defined as the property of a substance which is observed during a reaction where the chemical composition identity of the substance gets changed.

Physical property is defined as the property which can be measured and whose value describes the state of physical system. For Example: State, density etc.

Boiling point in the that value of the substance at which it changes its state from solid to liquid.

Reactivity is tendency of an substance to undergo any chemical reaction.

Density of the substance is the mass present in the unit volume of the substance.

Conductivity is the property of the substance to allow the flow of the electrons through them.

Boiling point, density and conductivity are the examples of physical properties.Where as reactivity is the is an example of chemical property.

a and b sometimes have a positive value