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AQA GCSE · Question 07.5 · Cell Biology
Why did the student dry the surface of each potato piece with a paper towel in step 5?
Why did the student dry the surface of each potato piece with a paper towel in step 5?
How to approach this question
The experiment aims to measure the change in mass of the potato due to water moving in or out of its cells. What would happen to the final mass reading if there were still drops of salt solution clinging to the outside of the potato piece?
Full Answer
To remove excess water/solution from the surface, so that only the change in mass of the potato itself is measured.
The purpose of this experiment is to measure the change in the mass of the potato tissue, which occurs due to the movement of water by osmosis. When the potato piece is removed from the solution, some liquid will be clinging to its surface. If this surface liquid is not removed, it will be included in the final mass measurement. This would add extra mass that is not part of the potato itself, leading to an inaccurate result for the change in mass. By gently blotting the surface dry, the student ensures that they are only measuring the mass of the potato.
Common mistakes
✗ Giving a vague answer like "to make it accurate" without explaining why.\n✗ Thinking it is to stop the osmosis process.
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