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A1.1.3—Cohesion of water molecules

Hydrogen bonds make water molecules cohere, producing continuous columns under tension and surface tension that living organisms exploit for transport and support.

Syllabus
First assessment 2025
Objective
A1.1.3
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceMay 2025
Most common paper—
Typical marks1–2

Common command terms

  • Identify
  • Explain
  • Outline

Scoring notes

Common mistake
Defining cohesion as attraction between water and another surface.

Recent exam appearances

May 2025Paper2 HL · TZ18(a)[ 4 ]A1.1.3—Cohesion of water molecules
May 2025Paper1A HL · TZ31[ 1 ]A1.1.3—Cohesion of water molecules
November 2023Paper1 HL · TZ24[ 1 ]A1.1.3—Cohesion of water molecules
November 2023Paper1 HL · TZ14[ 1 ]A1.1.3—Cohesion of water molecules
May 2019Paper2 HL · TZ14(b)[ 2 ]A1.1.3—Cohesion of water molecules
Practice this objective

Coverage 2019–2025 · Updated 14 Jul 2026

Concept essentials

  • Cohesion is attraction between water molecules.
  • Hydrogen bonding produces cohesive forces.
  • Cohesion maintains continuous water columns in xylem.
  • Surface tension is a consequence of cohesion at an interface.
ConceptIB Biology HL