Base your answer on the information below. Archimedes (287–212 BC), a Greek inventor and mathematician, made several discoveries important to science today. According to legend, Hiero, the king of Syracuse, commanded Archimedes to find out if the royal crown was made of gold, only. The king suspected that the crown consisted of a mixture of gold, tin and copper. Archimedes measured the mass of the crown and the total amount of water displaced by the crown when it was completely submerged. He repeated the procedure using individual samples, one of gold, one of tin, and one of copper. Archimedes was able to determine that the crown was not made entirely of gold without damaging it. Identify one physical property that Archimedes used in his comparison of the metal samples.