CAIE A Level Biology 9700 · Biological molecules

Biological molecules: describe question

Describe6 marksChallenge

Water is essential for life due to its unique properties arising from hydrogen bonding between water molecules. A marine biologist monitors a coral reef lagoon and a nearby shallow tide pool. The lagoon's water temperature remains between 26°C and 28°C throughout a hot day, whereas the tide pool fluctuates between 22°C and 34°C.

Describe how hydrogen bonding between water molecules gives water its high specific heat capacity, high latent heat of vaporisation, and solvent properties. Use these properties to explain why the lagoon provides a more stable environment for aquatic organisms than the tide pool.

0 words · 6 marks

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How this question is marked

6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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