O-Level Biology Osmosis Practical Guide: Potato and Visking Tubing

Study guide04 Nov 2025, 00:00 ZUpdated 17 Jul 2026

Reviewed by

Ezekiel Tan·Academic Advisor (Biology)

Q: What does this O-Level Biology osmosis practical guide cover?
A: It shows you how to run the Paper 3 potato and Visking tubing osmosis experiments, calculate percentage change, and evaluate the isotonic point properly.

TL;DR
Osmosis questions dominate the water-relations strand of the 6093 syllabus and almost always appear as paired setups (dialysis tubing plus plant tissue).
Nail your mass/length measurements, present percentage change tables with sig. figs, and give ACE commentary that links the gradient direction to cell turgor or plasmolysis.
Keep a bank of fair-test controls and improvement statements so you can answer every modification prompt.

Concrete example: Potato in concentrated sucrose loses mass because water moves out of the cells by osmosis.

Use this page after the broad O-Level Biology practical guide if you want the full Paper 3 context first.

For students who need weekly Paper 3 feedback, use O-Level Biology tuition Singapore after you have tested the checklist below.

Revisit the Full Experiment Bank

Pair this osmosis routine with the rest of our O-Level Biology Experiments collection so Paper 3 revision covers every standard skill block.

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Practise this in a lab

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Practical course record and certificate note

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Solution concentration / mol dm⁻³	Initial mass / g	Final mass / g	Change / g	% change	Qualitative notes
0.0 (distilled water)					Tissue firm, turgid finish.
0.2
0.4					Slightly flexible.
0.6
0.8					Wrinkled, flaccid appearance.

Evidence in the script	What to write next	Common weak answer to avoid
Final mass is lower than initial mass	Water moved out of the potato cells into the more concentrated external solution by osmosis.	The potato lost water because it was in sucrose.
The graph crosses 0% mass change	This concentration is the estimated isotonic point, where there is no net movement of water.	The graph shows no change.
Replicates differ near the isotonic point	Variation may come from uneven potato tissue, different blotting pressure, or timing differences.	There was human error.
A method improvement is required	Cut cores to the same diameter and length, blot with the same pressure, and add more concentrations around the zero crossing.	Use more accurate apparatus.

Step	What to do	What it proves
1	Calculate change in mass as final mass minus initial mass.	Whether the sample gained or lost water.
2	Calculate percentage change using the initial mass as the denominator.	Fair comparison between potato cylinders of different starting mass.
3	Plot percentage change against solution concentration.	The trend across the water-potential gradient.
4	Find where the curve crosses 0 percent change.	The estimated isotonic point, where there is no net water movement.
5	Evaluate scatter near the crossing.	Whether cutting, blotting, timing, or tissue variation could have shifted the estimate.

O-Level Biology Osmosis Practical Guide: Potato and Visking Tubing

Revisit the Full Experiment Bank

Practise this in a lab

2 | Parallel setups to rehearse

A. Visking tubing sugar-osmosis test

B. Potato strip or disc experiment

3 | Planning notes examiners look for

4 | PDO and ACE checkpoints

6093 Paper 3 osmosis checkpoint

Percentage change and isotonic point checkpoint

5 | Modification prompts you should anticipate

6 | Safety reminders

Sources

Revisit the Full Experiment Bank

Practise this in a lab

2 | Parallel setups to rehearse

A. Visking tubing sugar-osmosis test

B. Potato strip or disc experiment

3 | Planning notes examiners look for

4 | PDO and ACE checkpoints

6093 Paper 3 osmosis checkpoint

Percentage change and isotonic point checkpoint

5 | Modification prompts you should anticipate

6 | Safety reminders

Sources

2 | Parallel setups to rehearse

3 | Planning notes examiners look for

4 | PDO and ACE checkpoints

5 | Modification prompts you should anticipate

6 | Safety reminders