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Question 18M.3.HL.TZ2.b

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Date May 2018 Marks available [Maximum mark: 1] Reference code 18M.3.HL.TZ2.b
Level HL Paper 3 Time zone TZ2
Command term State Question number b Adapted from N/A
b.
[Maximum mark: 1]
18M.3.HL.TZ2.b

The graph shows the effect of relative humidity on the transpiration rate in Chinese privet (Ligustrum sinense).

The rate of water uptake was measured using the potometer shown in the diagram. The diameter of the capillary tube is 1 mm.

State a variable that needs to be controlled in this experiment.

[1]

Markscheme

temperature
OR
atmospheric pressure
OR
solar radiation/light
OR
wind speed
OR
leaf area
ORĀ 
size of plant

Do not accept humidity.