Chapter 12.4, Problem 31SSC

Interpretation Introduction

Interpretation:

Information supplied by a phase diagram must be described.

Concept introduction:

Phase diagram is a graphical representation of the phase change of a substance.

Answer to Problem 31SSC

Phase diagram gives melting point, boiling point of the substances along with the amount of heat energy supplied. It shows triple point and critical point of the substance.

Explanation of Solution

In phase diagram generally pressure is plotted along Y-axis and temperature is plotted long X-axis. The diagram shows the solid, liquid and gaseous state of the substance.

Temperature at which the vapor pressure of liquid is equal to vapor pressure of solid is the melting point of the substance. At this temperature there is no increase in temperature as latent heat is involved in phase change from solid to liquid. Again temperature increases and at certain temperature the vapor pressure of the liquid is equal to the atmospheric pressure. This is the boiling point of the substance at which liquid is converted to gaseous state without changing the temperature. Latent heat of vaporization is involved in this process. Again the temperature increases along with addition of heat energy.

Triple point is the temperature and pressure at which all the three phases i.e solid, liquid and gas coexist. Critical point is the temperature at which liquid is in equilibrium with gas.

Conclusion

Phase diagram gives information of states change of a substance with the help of heat energy. It shows also the melting point, boiling point, triple point and critical point of the substance.