Summarizing Cohesion and Adhesion in Liquids: Surface Tension and Capillary Action

Summary

• Attractive forces between molecules of the same type are called cohesive forces.
• Attractive forces between molecules of different types are called adhesive forces.
• Cohesive forces between molecules cause the surface of a liquid to contract to the smallest possible surface area. This general effect is called surface tension.
• Capillary action is the tendency of a fluid to be raised or suppressed in a narrow tube, or capillary tube which is due to the relative strength of cohesive and adhesive forces.

Glossary

adhesive forces

the attractive forces between molecules of different types

capillary action

the tendency of a fluid to be raised or lowered in a narrow tube

cohesive forces

the attractive forces between molecules of the same type

contact angle

the angle \(\theta \) between the tangent to the liquid surface and the surface

surface tension

the cohesive forces between molecules which cause the surface of a liquid to contract to the smallest possible surface area