Vivek Kumar

Water is the only liquid that becomes less dense as a solid. Density refers to the mass of a material per unit of volume, and density does change along with temperature. Even though the mass remains constant, the space or volume that it takes up also changes with temperature. As temperatures go up, so does the vibration of the material's molecules, leading to this drop in density. If someone sets ice in water or leaves it exposed to air, it starts melting sooner in the water, assuming that the water and air both have identical temperatures. The liquid water has molecules more tightly packed than those in the air, giving a higher level of contact with the ice and a swifter heat transfer rate. Add that to the fact that liquid water has a higher rate of heat transfer, and the explanation becomes clear.