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A1.1.4—Adhesion of water

Adhesion attracts water to other polar or charged surfaces, supporting capillary movement through narrow spaces such as soil pores and plant tissues.

Syllabus
First assessment 2025
Objective
A1.1.4
Level
SL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paper—
Typical marks1

Common command terms

  • Identify

Scoring notes

Common mistake
Using adhesion and cohesion as interchangeable terms.

Recent exam appearances

November 2025Paper1A SL · TZ31[ 1 ]A1.1.4—Adhesion of water

Coverage 2025–2025 · Updated 14 Jul 2026

Adhesion depends on what water is touching

Force Attractive contact Main biological consequence
Cohesion water ↔ water maintains a connected xylem column that can resist tension
Adhesion water ↔ polar or charged surface wets cellulose and pulls water along narrow spaces
Water molecules in a xylem vessel show cohesion between water molecules and adhesion between water and the vessel wall.

In narrow soil pores and spaces between cellulose fibres, adhesion pulls water along the hydrophilic wall. Cohesion draws neighbouring water molecules with it, producing capillary movement and keeping leaf cell walls moist.

Adhesion helps water enter and wet narrow spaces, but cohesion is the dominant force preventing a transpiring xylem column from breaking under tension.

Recover the chain from molecule to biological consequence

Unequal electron sharing + bent geometry → a polar molecule → hydrogen bonding and attraction to charged or polar matter. Begin every explanation from the interaction that produces the property.

Interaction or physical property Biological opportunity Constraint or boundary
water–water attraction xylem continuity; surface tension cohesion does not create transpiration pull
water–surface attraction capillary movement and wet cell walls adhesion is not the main force resisting xylem tension
attraction to ions and polar solutes reactions, diffusion and transport non-polar O₂ and N₂ remain poorly soluble
heat capacity, conductivity, buoyancy and viscosity stable habitat, support and propulsion heat loss, diving cost and drag require adaptations

Recognise adhesion from the contact pair

[ 1 ]

Which of the following is a consequence of the adhesive properties of water?

Concept essentials

  • Adhesion is attraction between water and another surface.
  • Water adheres well to polar or charged materials.
  • Adhesion and cohesion act together during capillary movement.