Question

Describe the molecular basis of the property of water responsible for the presence of ice on the surface of a frozen lake.

Short answer

On lowering the temperature, the kinetic energy of the liquid water molecules decreases, thus leading to a more arranged structure of water, i.e., ice. Thus, ice is present on the surface of the frozen lake.

Step-by-step solution

Effect of temperature on the liquid water

On decreasing the temperature, the kinetic energy of the molecules is compensated for the increase in the potential energy. Thus, the water molecules are more arranged in a hexagonal 3-D array to provide a more compact structure of ice.

Difference in the density

Now, in this low temperature, more and more arrangements are taking place, with four molecules of water surrounded by one molecule of water. But this arrangement leads to a decrease in the density of ice, thus ice is seen on the surface of a frozen lake.