Chapter 13, Problem 81A

Interpretation Introduction

Interpretation: The effect of the opening windshield in defogging a car is to be explained.

Concept introduction:

When water vapor, or water in its gaseous state, condenses, fog forms. The condensation process turns water vapor molecules into tiny liquid droplets that float in the air.

Answer to Problem 81A

The freezing point increases marginally with increased pressure.

Explanation of Solution

Outside air is cold and dry whereas inside car air is humid and warm.

A car's windscreen can be opened to clear the fog. The defogging occurs by replacing humid air inside the car with drier air present outside the car.