A1.1 Water
Water’s polarity and hydrogen bonding create solvent, thermal, cohesive and adhesive properties that support metabolism, transport, cooling and aquatic life.
- Syllabus
- First assessment 2025
- Topic
- A1.1
- Level
- SL
Exam analysis
Chance of appearing21%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–2
Most tested objectives
Common question formats
- Definition or recall
- Diagram interpretation
- Process explanation
- Comparison
- Data analysis
- Structured response
Recent exam appearances
November 2025Paper2 SL · TZ37(a)[ 4 ]A1.1.2—Hydrogen bonds in water
November 2025Paper2 SL · TZ13(e)[ 2 ]A1.1.2—Hydrogen bonds in water
November 2025Paper1A SL · TZ11[ 1 ]A1.1.6—Physical properties of water for aquatic animals
November 2025Paper1A SL · TZ31[ 1 ]A1.1.4—Adhesion of water
May 2025Paper2 SL · TZ16(a)[ 4 ]A1.1.3—Cohesion of water molecules
Practice this topic
Coverage 2010–2025 · Updated 14 Jul 2026
Objective notes
6 learning objectives• First cells originated in water, where oceans shielded early life from UV radiation
• Water remains the medium for most life processes and forms much of cell mass
• O-H covalent bonds and water's V-shape make molecules polar
• Hydrogen bonds form between water molecules, not within a molecule
• Hydrogen bonding explains many unusual water properties
• Hydrogen bonding creates cohesion and surface tension
• Cohesion prevents xylem water columns breaking under tension
• Surface tension supports droplets and surface-skating insects
• Water adheres to polar or charged surfaces
• Adhesion supports capillary action in soil channels and cellulose cell walls
• Cohesion is the stronger force in xylem transport; adhesion helps refill vessels
• Water dissolves ions and polar molecules by hydration and hydrogen bonding
• Aqueous solution enables diffusion, transport, enzyme activity, and metabolism
• Non-polar molecules are hydrophobic; O₂ and N₂ have low solubility in water
• Specific heat capacity stabilizes aquatic temperatures and body temperature
• Thermal conductivity, buoyancy, and viscosity shape aquatic adaptations
• Compare black-throated loon and ringed seal adaptations for diving, insulation, and movement