DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ1.6a

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Date May 2022 Marks available [Maximum mark: 3] Reference code 22M.2.SL.TZ1.6a
Level SL Paper 2 Time zone TZ1
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 3]
22M.2.SL.TZ1.6a
(a)

Outline how the properties of water make it an effective coolant for the body.

[3]

Markscheme
  1. hydrogen bonds hold water molecules together/make water molecules cohere;
  2. evaporation requires breaking of hydrogen bonds / heat needed to break hydrogen bonds
  3. water has a high heat of vaporization/high latent heat;
  4. evaporation of water/sweat removes heat from/cools the skin/body;
Examiners report

This question revealed widespread misunderstanding of the properties of water and changes of state. Most candidates though that water's high specific heat capacity explains its role as a coolant and that sweat cools the body by taking heat from it to raise its temperature. Few candidates referred to the requirement for heat to break hydrogen bonds as water evaporates. To be able to understand biological processes properly, a firm grounding in physics and chemistry is needed, but all too often it was lacking.

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