Chapter 2, Problem 12RQ

Summary Introduction

Introduction:

The cohesive force that occurs at the liquid-gas interface through which the liquid molecules are strongly attracted to the molecules in the bulk of the liquid is termed as surface tension. Laplace’s law describes that the distending pressure of a liquid sphere is directly proportional to the surface tension of the liquid and inversely proportional to the radius of the sphere. This law is also applied to the alveoli of lungs because the alveoli are also in contact with each other and there also exists a surface area, which is the intra-alveolar surface area. The equation of Laplace’s law is:

$\text{Pressure, P}=\frac{\text{2ST}}{\text{r}}$

Where ST is the surface tension measured in dynes per centimeters and r is the radius of the liquid sphere in centimeters.