Ever wondered why chips go soggy when you leave them...
Comprehensive Guide to Osmosis Practical for AQA GCSE Science

Setting Up Your Osmosis Experiment
You'll be investigating osmosis - the movement of water molecules from areas of high concentration to low concentration through a semi-permeable membrane. Think of it like water always trying to balance itself out on both sides of a barrier.
Start by cutting five identical potato cylinders using a cork borer, then trim the ends so they're all exactly the same length. Weigh each cylinder carefully - accuracy matters here! You'll need five different concentrations of sugar solution in separate test tubes, from pure water (0.0 mol/dm³) to a strong sugar solution (1.0 mol/dm³).
Pop one potato cylinder into each tube and leave them for the same amount of time. When you remove them, blot them dry before weighing - any surface water will mess up your results.
Top Tip: Keep your potato cylinders the same size and timing consistent - small changes can throw off your entire experiment!

Understanding Your Results
The magic happens when water moves to balance concentrations on both sides of the potato cell membranes. In distilled water, your potato gained 16.2% mass because water rushed into the cells where sugar concentration was higher - this is called a hypotonic solution.
As sugar concentration increases outside the potato, less water moves in. Eventually, you'll hit a point where water actually leaves the potato cells. In the strongest solutions, the potato lost 9% of its mass because the outside solution was hypertonic - more concentrated than inside the cells.
The graph shows this perfectly - mass gain drops steadily until it crosses zero, then becomes mass loss. Where the line crosses zero tells you the concentration that matches inside the potato cells.
Exam Smart: Remember that water always moves towards higher solute concentration - if there's more sugar outside, water moves out of the potato!
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Comprehensive Guide to Osmosis Practical for AQA GCSE Science
Ever wondered why chips go soggy when you leave them out, or why your fingers wrinkle in the bath? It's all down to osmosis - the movement of water through cell membranes. This practical investigation shows you exactly how to...

Setting Up Your Osmosis Experiment
You'll be investigating osmosis - the movement of water molecules from areas of high concentration to low concentration through a semi-permeable membrane. Think of it like water always trying to balance itself out on both sides of a barrier.
Start by cutting five identical potato cylinders using a cork borer, then trim the ends so they're all exactly the same length. Weigh each cylinder carefully - accuracy matters here! You'll need five different concentrations of sugar solution in separate test tubes, from pure water (0.0 mol/dm³) to a strong sugar solution (1.0 mol/dm³).
Pop one potato cylinder into each tube and leave them for the same amount of time. When you remove them, blot them dry before weighing - any surface water will mess up your results.
Top Tip: Keep your potato cylinders the same size and timing consistent - small changes can throw off your entire experiment!

Understanding Your Results
The magic happens when water moves to balance concentrations on both sides of the potato cell membranes. In distilled water, your potato gained 16.2% mass because water rushed into the cells where sugar concentration was higher - this is called a hypotonic solution.
As sugar concentration increases outside the potato, less water moves in. Eventually, you'll hit a point where water actually leaves the potato cells. In the strongest solutions, the potato lost 9% of its mass because the outside solution was hypertonic - more concentrated than inside the cells.
The graph shows this perfectly - mass gain drops steadily until it crosses zero, then becomes mass loss. Where the line crosses zero tells you the concentration that matches inside the potato cells.
Exam Smart: Remember that water always moves towards higher solute concentration - if there's more sugar outside, water moves out of the potato!
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