Question 4
FA student investigated the effect of the size of a cube on diffusion.
The student cut three cubes of different sizes from a block of pink agar jelly. The pink colour disappears when acid diffuses into the jelly.
The student placed the cubes in a beaker of dilute acid. The student timed how long it took for each cube to become completely colourless.
The Figure shows the apparatus.
Figure
The Table shows the results.
Table
| Length of side of cube in cm | Surface area : volume ratio | Time taken to become colourless in minutes |
|---|---|---|
| 0.5 | Z | 3 |
| 1 | 6:16:16:1 | 11 |
| 2 | 3:13:13:1 | 44 |
a.[1]
Give the independent variable in this investigation.
b.[2]
Give two variables that the student should control.
c.[2]
Calculate value Z.
Give your answer in the form n:1n:1n:1.
d.[3]
Explain the results.
8.1 Exchange surfaces and diffusion Questions
42 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.