Chapter 12, Problem 77A

Interpretation Introduction

Interpretation:

The term melting point must be defined.

Concept introduction:

Melting is a process in which solid is converted to liquid.

Answer to Problem 77A

Melting point is the temperature at which solid is converted to liquid and the temperature remain constant until the whole solid is not converted to liquid.

Explanation of Solution

At melting point no temperature is changed as latent heat is involved for the phase change.

At melting point solid is in equilibrium with liquid. The vapor pressure of solid is equal to vapor pressure of the liquid.

For example normal melting point of ice is 0°C.

Melting point decreases in presence of impurity.

Melting point of ice is less than 0°C when salt is added with ice.

Conclusion

Melting point of a liquid is the temperature at which the vapor pressure of solid is equal to vapor pressure of the liquid.