Chapter 8, Problem 8.114GP

(a)

Interpretation Introduction

Interpretation:

The explanation for skating on ice has to be given based on phase diagram for water.

Concept introduction:

Phase diagrams:

The different phases of a system can be represented in a diagram called a phase diagram. The phase diagram of ${\text{H}}_{\text{2}}\text{O}\text{and}{\text{CO}}_{\text{2}}$. are examples of phase diagrams for a single component system. The coordinates of these diagrams are usually pressure and temperature.

Phase diagram of water:

Solid ice is stable at low temperature and liquid water is stable at moderate temperature and high pressure. At high temperature and low pressure, gas phase is the stable one.

(b)

Interpretation Introduction

Interpretation:

Skating on dry ice is possible or not has to be determined.

Concept introduction:

Phase diagrams:

The different phases of a system can be represented in a diagram called a phase diagram. The phase diagram of ${\text{H}}_{\text{2}}\text{O}\text{and}{\text{CO}}_{\text{2}}$. are examples of phase diagrams for a single component system. The coordinates of these diagrams are usually pressure and temperature.

Phase diagram of carbon dioxide:

At a pressure of $\text{5}\text{.2}\text{atm}\text{and}\text{216}\text{.6}\text{K}$, the triple point of ${\text{CO}}_{\text{2}}$ occurs. When the vapour pressure of solid ${\text{CO}}_{\text{2}}$ is $\text{1}\text{atm}$, the liquid phase is not stable and solid sublimates and this solid ${\text{CO}}_{\text{2}}$ is called dry ice.