Want to See Osmosis in Action? A Simple Potato Experiment
Osmosis is one of those core Biology ideas that students hear about early, but often struggle to really “see.” It’s the movement of water molecules across a partially permeable membrane, from a region of high water concentration to one of lower water concentration. Sounds simple enough—until it appears as a six-mark exam question!
At Hemel Private Tuition, we prefer to make Biology hands-on and visual. One of the easiest ways to watch osmosis in action is with a potato, some sugar solutions, and a little careful measurement.
Setting Up the Experiment
To make sure the test is fair, we need identical potato chips. We use a chipper to cut them so they’re all the same width, then trim them to the same length. Each chip is then weighed on an accurate balance before being placed into a beaker of sugar solution of known concentration.
Typical solutions might include:
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Distilled water (0% sugar)
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Weak sugar solution (e.g. 0.1 mol/dm³)
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Medium sugar solution
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Strong sugar solution
The chips sit in the solutions for about an hour, long enough for osmosis to take place.
Recording the Changes
Once the hour is up, we blot the chips dry and take three types of measurements:
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Mass change – using an accurate balance
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Length change – with a ruler
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Width (girth) change – measured precisely using Vernier callipers
By comparing before and after measurements, students can see the effect of osmosis directly:
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In dilute solutions (more water outside the chip), the potato gains mass and length as water enters the cells.
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In concentrated solutions (less water outside), the chip shrinks as water leaves the cells.
What Students Learn
This experiment demonstrates that osmosis isn’t just an abstract definition—it’s something you can measure and observe. By plotting the percentage change in mass against the sugar concentration, students can even estimate the concentration of cell sap inside the potato.
It’s a perfect example of how Biology combines theory with data, measurement, and analysis. Students gain experience in:
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Controlling variables to keep the test fair
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Using accurate scientific equipment (balances and callipers)
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Analysing data and drawing a valid conclusion
Why We Teach This Way
At Hemel Private Tuition, we believe students learn best when they do science, not just read about it. This practical shows osmosis clearly, makes exam questions easier to answer, and helps students build real scientific skills.
If your child is preparing for GCSE or A-Level Biology and could benefit from more hands-on, guided learning, we’d love to help.
👉 Contact Philip M Russell Ltd – Hemel Private Tuition to book a lesson today.
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