Fiducia TogetherStandard practicals: osmosis
The potato chip experiment, and why percentage change is used.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Chips of plant tissue are placed in solutions of different concentration and the change in mass measured.
Where it applies
GCSE biology and combined science, as a required practical.
How it works
Mass increases where the solution is more dilute than the cell contents and decreases where it is more concentrated. The concentration at which there is no change estimates the cell's own.
Percentage change is used because the starting masses differ, so raw change is not comparable.
How to use it in your work
Calculate PERCENTAGE change in mass. Raw change loses the mark.
Dry the chips consistently before weighing and say so — surface water is the main error.
On the graph, the x-intercept is the estimated internal concentration. Say what it represents.
Where to get help
Your teacher and your board's specification and mark scheme.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.