Adhesive forces

Definition

Adhesive forces are the attractive interactions between unlike molecules. These forces are responsible for phenomena such as capillary action and the spreading of liquids on solid surfaces.

5 Must Know Facts For Your Next Test

1. Adhesive forces occur between different types of molecules, unlike cohesive forces which occur between like molecules.
2. They play a crucial role in capillary action, where liquid rises or falls in a narrow tube due to the attraction between the liquid and the tube material.
3. The strength of adhesive forces depends on the nature of the interacting substances; for example, water has strong adhesive forces with glass but weaker ones with non-polar surfaces like oil.
4. Adhesive forces are essential in various applications such as painting, gluing, and ink printing, where liquid needs to spread over or stick to a surface.
5. These forces can be quantified using contact angle measurements; a low contact angle indicates strong adhesive forces between the liquid and solid.

Review Questions

• What is the main difference between adhesive and cohesive forces?
• How do adhesive forces contribute to capillary action?
• Why is it important to understand adhesive forces in applications like painting or gluing?

Related terms

Cohesive Forces: Attractive interactions between identical molecules within a substance.

Capillary Action: The ability of a liquid to flow in narrow spaces without external forces due to adhesive and cohesive interactions.

Contact Angle: $\theta$ is the angle formed by a liquid at the boundary where it meets a solid surface; used to quantify wetting properties influenced by adhesive forces.