Osmosis · 3 parts · syllabus 3.2

Why does a limp lettuce leaf go crisp in water?

Cut potato cylinders, weigh them, soak them in water and five sucrose solutions, and weigh them again. Work out the percentage changes, find the concentration with no net movement of water, then bend the cylinders and look at their cells.

Start learning Explore the experiment

Two lettuce leaves on a plate: one limp and folded, one crisp after standing in a glass of water.

Follow the idea

Water and membranes
Water as a solvent, partially permeable membranes and osmosis, with dialysis-tubing bags
Not started
Potato in sugar solutions
Plant tissue in solutions of different concentrations: the potato investigation, turgor and plasmolysis
Not started
Water for whole organisms
Water potential in organisms: root hairs, wilting, red blood cells and food that keeps
Not started

A rack of six short glass tubes of clear liquid, each with a potato cylinder standing covered at the bottom; half a potato, a cork borer, a scalpel, forceps, a paper towel and a balance in front.

The experiment · Potato cylinders in sucrose solutions · weigh them, find the zero point, bend them

Run it yourself, or project it for the class

Use the apparatus step by step and look closely at what happens. The whole experiment fits one screen, so it works on a projector too.

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Final check

Explain it on your own across all three parts. Hints and keys stay closed until you submit.

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Return and recall

Come back after one to two weeks and answer with the lesson closed.

Recall questions

For teachers

Printable worksheets with their answer keys, the final check and the return questions for this module.

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Scope and sources

Cambridge IGCSE Biology 0610 · 2026–2028 v3 · Original learning materials.

Water as a solvent (3.2.1); osmosis through partially permeable membranes, in terms of water potential (3.2.2, Supplement 3.2.7); dialysis tubing (3.2.4) as a data investigation in the reading and practice; water entering and leaving cells (3.2.3) and plant tissue in sucrose solutions (3.2.5) through the potato-cylinder practical; support by turgor (3.2.6) with turgid, flaccid and plasmolysis (Supplement 3.2.8); water uptake and loss by organisms (Supplement 3.2.9). Masses in the experiment come from a teaching model.

Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.

Official Cambridge syllabus

Why does a limp lettuce leaf go crisp in water?

Follow the idea

Water and membranes

Potato in sugar solutions

Water for whole organisms

Run it yourself, or project it for the class