Chapter 10, Problem 45A

Interpretation Introduction

Interpretation:

The change in the molecule needs to be explained if steam at 150°C is cooled slowly until it liquefies and then solidifies.

Concept Introduction:

Physical state change of a matter occurs when the intermolecular force is changed with external parameters like heat, pressure etc.

Answer to Problem 45A

Intermolecular forces of water molecule increases and the intermolecular distances decreases when steam at 150°C is cooled slowly until it liquefies and then solidifies.

Explanation of Solution

Kinetic energy of molecule is directly proportional to the absolute temperature.

If temperature is decreased then kinetic energy decreases and molecules start coming closer. As a result the intermolecular distance decreases and intermolecular force increases. Thus steam is first converted to liquid water in which intermolecular force is more than gas steam but less than ice. When it is cooled further then intermolecular distance decreases and intermolecular force of water molecule increases.

Conclusion

When steam at 150°C is cooled slowly until it liquefies and then solidifies then intermolecular distance of water molecule decreases and intermolecular force increases.