ensity is a physical property that represents the compactness of a substance. It is defined as the mass of a substance per unit volume. The higher the density, the more mass is packed into a given volume.

Gold is known for its high density. It is a dense metal with a density of approximately 19.3 grams per cubic centimeter (g/cm³). This makes gold denser than both steel and mercury.

Steel, which is an alloy primarily composed of iron and carbon, has a lower density than gold but is still relatively dense compared to many other materials. The density of steel varies depending on its composition, but it typically ranges from around 7.7 g/cm³ to 8.1 g/cm³.

Mercury is a liquid metal at room temperature and has a relatively low density compared to both gold and steel. Its density is approximately 13.6 g/cm³, making it less dense than gold but denser than steel.

Therefore, the correct sequence of the substances in decreasing order of density is Gold > Steel > Mercury.