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CAIE A-Level Biology 4.2.5 Investigating Water Potential

Practise placing equal plant-tissue samples in a concentration series, controlling exposure and blotting, then using percentage change and the zero-change point to estimate water…

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • prepare equal tissue samples and a suitable range of accurately known solution concentrations
  • control immersion time and temperature, then blot samples consistently before remeasuring
  • plot percentage change and estimate the isotonic concentration at zero net change

4.2.5—Water potential investigation question 1

[Maximum number: 1]

Four cylinders that were identical in size, A, B, C and D, were cut from potatoes that had been stored for different lengths of time.

The cylinders were weighed, immersed in 10\% salt solution for 45 minutes and then reweighed.
The percentage change in mass was then calculated.
Which cylinder had a water potential similar to the 10 % salt solution?

percentage

change in mass

-7.2

-2.5

-0.9

+3.4

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