Chapter 21, Problem 18A

Ice is less dense than water because of its open crystalline structure. But why is water at $0°C$ less dense than water at $4°C$?

To determine

The reason that the water at $0^0\text{C}$ is less dense that the water at $4^0\text{C}$ .

Explanation of Solution

Introduction:

Measurement of mass per unit volume is termed as density. The freezing temperature of the water at atmospheric pressure is $0^0\text{C}$ .

As given in the statement, density of ice is less as compared to water because of the crystalline structure of the ice. When ice melts into water, the crystalline structure of the ice breaks and increases the density of the water. At $0^0\text{C}$ , water still contains some of the ice-like clusters which results in decreasing density of the water.

Furthermore, as the temperature increases, molecules slow down their movement and the density of the water is greater at $4^0\text{C}$ .

Conclusion:

Thus, the density of the water is less at $0^0\text{C}$ .