Cohesive forces

Definition

Cohesive forces are the intermolecular forces that hold molecules of the same substance together. These forces are responsible for phenomena like surface tension in liquids.

5 Must Know Facts For Your Next Test

1. Cohesive forces result from attractions between similar molecules, such as hydrogen bonding, Van der Waals forces, and dipole-dipole interactions.
2. Surface tension is a direct consequence of cohesive forces acting at the surface of a liquid.
3. In liquids, cohesive forces cause molecules to be attracted to each other and resist separation.
4. Cohesive forces are generally stronger in liquids with higher boiling points due to stronger intermolecular interactions.
5. Mercury exhibits very high cohesive forces, which is why it forms beads rather than spreading out on surfaces.

Review Questions

• What role do cohesive forces play in surface tension?
• How do cohesive forces affect the boiling point of a liquid?
• Describe an example where strong cohesive forces can be observed.

Related terms

Adhesive Forces: Intermolecular forces that occur between different substances, causing them to stick together.

Hydrogen Bonding: A type of strong intermolecular force occurring between molecules containing hydrogen bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.

Surface Tension: The elastic tendency of a fluid surface caused by cohesive forces, making it acquire the least surface area possible.