Why does kerosene float on the surface of water, and water on the surface of mercury?

Indeed, kerosene floats on the surface of the water. This is due to the fact that these substances have different densities: water – 998 (kg / m ^ 3), kerosene – 800 (kg / m ^ 3). According to the laws of physics, a body with a lower density will always float on the surface of another. Similarly, water floats on the surface of mercury: water – 998 (kg / m ^ 3), mercury – 13,500 kg / m ^ 3, which, in comparison with water, has a much higher density and will push water to the surface.