Chapter 10, Problem 22A

Interpretation Introduction

Interpretation: The change that occurs in the molecules when sample of ice is slowly heated until it liquefies and then vaporizes is to be stated.

Concept introduction:The energy of molecules increases as the temperature of substance increase. The phase change occurs when ice is subjected to heat.

Answer to Problem 22A

The intermolecular distance between molecules of water increases and the intermolecular forces between molecules decreases whensample of ice is slowly heated until it liquefies and then vaporizes.

Explanation of Solution

Water in the shape of ice is categorized as solid state. In solid state, molecules are present very close to each other. In ice, water molecules are strongly held together by hydrogen bonding. When ice is subjected to high temperature the molecules of water starts vibrating. The vibration of molecules breaks structure of ice. The hydrogen bond between molecules starts breaking. Slowly as the temperature increases the molecules of water becomes independent. Now they are not held by strong hydrogen bonds.At melting point the ice phase of water changes from solid to liquid.

Ice liquefies when hydrogen bond between molecules break. They start moving in random direction. As the applied heat increases temperature, the movement of molecules increases. When the temperature reaches about $373\text{K}$ the molecules of water becomes vapors. At this temperature phase of water changes from liquid to gas. In gaseous state, molecules are present at very far distance from each other. The intermolecular forces of attraction and repulsion are negligible. The molecules of water in gaseous state are always in random motion.

Conclusion

The intermolecular distance between molecules of water increases and the intermolecular forces between molecules decreases whensample of ice is slowly heated until it liquefies and then vaporizes.