Chapter 15, Problem 110A

(a)

Interpretation Introduction

Interpretation: To determine the effect of boiling point by increasing pressure.

Concept Introduction: The point at which atmospheric pressure equals vapor pressure is known as the boiling point. It can be denoted by ${\text{T}}_{\text{b}}$ .

Answer to Problem 110A

(b )

Explanation of Solution

The boiling point of water increases along with pressure. Since vaporization occurs when molecules are moving more rapidly apart from each other and below increased pressure, adding an external force to the surface of the water causes the molecules to remain closer together and requires more energy to vaporize.

(b)

Interpretation Introduction

Interpretation: To determine the effect of boiling point by decreasing pressure.

Concept Introduction: The point at which atmospheric pressure equals the vapor pressure is known as the boiling point (or air pressure as you have mentioned). There are always some particles in a liquid with enough energy to move into the gas phase. Additionally, gaseous particles are re-entering the liquid.

Answer to Problem 110A

By decreasing the pressure, the water’s boiling point decreases.

Explanation of Solution

Water's boiling point is influenced by atmospheric pressure. The boiling point rises as atmospheric pressure does; conversely, the boiling point falls as atmospheric pressure falls (as it does as elevation rises). This is because by decreasing pressure, water molecules become apart from each other and less energy is required to vaporize them.