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A1.1.5—Solvent properties of water

Water’s partial charges surround ions and interact with polar molecules, allowing many biologically important solutes to dissolve and move in aqueous fluids.

Syllabus
First assessment 2025
Objective
A1.1.5
Level
SL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2018
Most common paper—
Typical marks1–3

Common command terms

  • Identify
  • Explain

Scoring notes

Common mistake
Calling water a universal solvent that dissolves all substances.

Recent exam appearances

May 2018Paper1 SL · TZ17[ 1 ]A1.1.5—Solvent properties of water
November 2017Paper2 SL · TZ03(b)[ 3 ]A1.1.5—Solvent properties of water
November 2016Paper1 SL · TZ08[ 1 ]A1.1.5—Solvent properties of water
November 2014Paper1 SL · TZ07[ 1 ]A1.1.5—Solvent properties of water
Practice this objective

Coverage 2014–2018 · Updated 14 Jul 2026

Water Dissolves Polar and Ionic Solutes

Water dissolves many ionic and polar substances because its partial charges attract ions and polar regions of molecules.

Water molecules form hydration shells around ions and hydrogen bonds with many polar solutes. Dissolved particles remain mobile, so they can be transported in blood, xylem or phloem and can take part in enzyme-catalysed reactions in aqueous solution.

Hydrophilic substances interact with water and tend to dissolve. Hydrophobic substances are non-polar and tend to remain separate; this insolubility is important for structures such as lipid membranes.

When sodium chloride dissolves, the oxygen side of water faces Na+ and the hydrogen sides face Cl-, producing hydration shells that keep the ions dispersed.

Water is not a literally universal solvent. Many non-polar substances dissolve poorly, and solubility does not mean that a substance is harmless.

Solvent properties of water

Assessment in practice

1–3 marks
How it is assessed

This objective is assessed through structured response, multiple choice, commonly using Identify / Explain.

Command terms

Identify / Explain

What earns marks

Exam questions commonly ask students to connect solvent behaviour to polarity, identify a biological transport example, or distinguish solvent properties from cohesion and thermal properties.

Watch for

Calling water a universal solvent that dissolves all substances.

Representative question

Question 1

[Maximum number: 3]

Water has important solvent properties. Explain these properties using an example to illustrate your answer.

Water summary

  • Water is life's medium because substances can dissolve, move and react in it.
  • Unequal electron sharing and bent geometry make water polar; hydrogen bonds form between molecules.
  • Many hydrogen bonds produce cohesion, maintaining xylem columns and creating surface tension.
  • Adhesion is water-to-surface attraction and contributes to movement through narrow soil spaces and cellulose walls.
  • Polarity lets water hydrate ions and interact with polar solutes; dissolved particles can be transported and react, while non-polar substances are hydrophobic.
  • Compared with air, water provides more buoyancy and drag, transfers heat faster and changes temperature more slowly. Aquatic adaptations respond to these consequences.

Concept essentials

  • Polarity allows water to interact with ions and polar molecules.
  • Water molecules form oriented hydration shells around ions.
  • Many dissolved solutes can be transported in aqueous body fluids.
  • Non-polar substances generally dissolve poorly in water.