36 exam-style questions on Water — topic A1.1 of Unity and diversity in the IB Biology syllabus — with answers and explanations. Samples below; the full set is free with an account.
State the term for the attractive force between water molecules and the hydrophilic walls of a xylem vessel.
Answer: Adhesion
Adhesion is the attraction between water and a different (polar) surface, whereas cohesion is the attraction between water molecules themselves.
Explain why sodium chloride dissolves readily in water.
Answer: Polar water molecules surround the separated ions
The partial charges on polar water molecules form hydration shells around Na⁺ and Cl⁻, keeping the ions apart and in solution.
Identify the property of water, arising from cohesion, that allows some insects to move across a pond surface without sinking.
Answer: Surface tension
Hydrogen bonding pulls surface molecules together, creating surface tension strong enough to support small insects.
Determine the advantage to aquatic organisms of water's high specific heat capacity.
Answer: It keeps aquatic temperatures relatively stable
A large amount of energy is needed to change the temperature of water, so aquatic habitats remain thermally stable.
Water is transported up the xylem as a continuous column. Identify the combination of properties that makes this possible.
Answer: Cohesion and adhesion
Cohesion holds the water column together while adhesion to the vessel walls helps counteract gravity (the cohesion-tension mechanism).
Explain why sweating is an effective cooling mechanism in mammals.
Answer: High latent heat of vaporisation
Breaking the many hydrogen bonds to evaporate water removes a large amount of heat energy from the skin, cooling the body.
That was 6 of 36 Water questions.
Practise all 36 freeStateAO1 · 1–2 marks
One word or one short sentence. No explanation, no working: the mark is for the fact itself.
ExplainAO3 · 3–8 marks
Give reasons or causes: say what happens AND why, linking each step with 'because' or 'so that'.
OutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
36 Water questions — free with an account. Spaced repetition, streaks and full exam simulations included.
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