C

Cohesive Forces

Cohesion ∝ γ (surface tension); W_cohesion = 2γ
Quick Reference
Formula / NotationCohesion ∝ γ (surface tension); W_cohesion = 2γ
Also Known AsCohesion, intermolecular cohesion, self-adhesion, surface tension (related)

What is Cohesive Forces?

Cohesive forces are the intermolecular attractive forces between like molecules in a substance. These forces are responsible for surface tension and the tendency of liquids to minimise their surface area. Water has exceptionally high cohesive forces due to hydrogen bonding, which explains its high surface tension. Cohesive forces compete with adhesive forces in determining capillary action behaviour.

Formula & Notation

Cohesion ∝ γ (surface tension); W_cohesion = 2γ

Other Names / Synonyms: Cohesion, intermolecular cohesion, self-adhesion, surface tension (related)

Properties & Characteristics

Cohesive forces are intermolecular attractive forces between like molecules within a substance (as opposed to adhesive forces between unlike molecules). In liquids, cohesion gives rise to surface tension and resists vaporisation. Water has exceptionally high cohesion due to hydrogen bonding (surface tension = 72.8 mN/m at 25°C). Cohesion is responsible for the formation of spherical droplets and the meniscus in narrow tubes.

Uses & Applications

Cohesive forces determine the physical properties of liquids: surface tension (used in emulsification, flotation, detergency), viscosity, and capillary behaviour. Understanding cohesion guides the design of surfactants, adhesives, coatings, and inkjet printing systems.

Safety Information

High surface tension of water can cause liquids to bridge narrow gaps in industrial processes, potentially blocking flow. Strong cohesion in mercury makes it form isolated droplets that are hard to collect if spilled — mercury spills require specialised cleanup to prevent vapour inhalation.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Cohesive Forces
Formula Cohesion ∝ γ (surface tension); W_cohesion = 2γ
Synonyms Cohesion, intermolecular cohesion, self-adhesion, surface tension (related)

Frequently Asked Questions

Cohesive forces are the intermolecular attractive forces between like molecules in a substance. These forces are responsible for surface tension and the tendency of liquids to minimise their surface area. Water has exceptionally high cohesive forces due to hydrogen bonding, which explains its high surface tension. Cohesive forces compete with adhesive forces in determining capillary action behaviour.

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