Chapter 12, Problem 12.1P

Interpretation Introduction

Interpretation:

The energy of attraction between particles compare with their energy of motion in a gas and in a solid is to be determined. Also, two macroscopic properties that differ between a gas and a solid are to be identified.

Concept introduction:

The phase is defined as the physical state of a substance. The properties of a phase are determined by the interaction of the potential energy $\left(E_p\right)$ and kinetic energy $\left(E_{\text{k}}\right)$ of particles. There are three major phases as follows:

1) Solid

2) Liquid

3) Gas

Potential energy $\left(E_p\right)$ tries to keep the molecules together and act as the intermolecular forces while kinetic energy $\left(E_{\text{k}}\right)$ is associated with the motion and tries to move apart the molecules.

Answer to Problem 12.1P

In gases, the value of kinetic energy $\left(E_{\text{k}}\right)$ is greater than potential energy $\left(E_p\right)$ so the particles can move freely without any force of attraction towards each other while in the case of solids, the value of $E_p$ is greater than $E_{\text{k}}$ so the solid particle can not move freely and remain vibrating at one place. The two macroscopic properties that differ between a gas and a solid are volume and compressibility.

Explanation of Solution

The energy of attraction between particles is the potential energy and energy of motion is kinetic energy. In gases, the value of kinetic energy $\left(E_{\text{k}}\right)$ is greater than potential energy $\left(E_p\right)$ so the particles can move freely without any force of attraction towards each other while in the case of solids, the value of $E_p$ is greater than $E_{\text{k}}$ so the solid particle can not move freely and remain vibrating at one place.

The two macroscopic properties that differ between a gas and a solid are volume and compressibility.

In gases, the particles can move easily so they take the shape of the container in which they are filled and therefore there is no constant volume. On the other hand, solids have fixed volume and not depend upon the shape of the container in which they are placed.

Gases have high compressibility because the particles can move easily and there is not fixed shape while solids have fixed shape and more interaction between the particles than gases so there is no compressibility.

Conclusion

The properties of a phase are determined by the interaction of the potential energy $\left(E_p\right)$ and kinetic energy $\left(E_{\text{k}}\right)$ of particles. The two macroscopic properties that differ between a gas and a solid are volume and compressibility.