Which is most likely a chemical property? Oxidation state: the charge an atom has if it was bonded ionically to other atoms. Different oxidation states indicate different abilities to bond with other atoms.
Melting point: the temperature at which a solid turns into a liquid. Different substances have different melting points.
Density: the amount of a substance that fits in a certain volume. Different states of matter of the same substance can have different densities.
Conductivity: the ability to transfer electrical charges. Conductivity is different in different substances.