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Concentration Gradient and Potato Mass
A student investigated the effect of concentration of salt solution on the mass of uncooked potato pieces. Figure 4 shows the results.
Explain why the result for the potato pieces at 1.0 mol/dm³ was different from the result at 0.6 mol/dm³.
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Marking points
- 1 States that more water left, or more outward osmosis occurred, at 1.0 mol/dm³.
- 2 Links this to the steeper concentration gradient or greater inside–outside concentration difference.
Full-mark answer
The 1.0 mol/dm³ solution created a larger concentration difference between the outside solution and the potato cells. This steeper gradient caused more water to leave the cells by osmosis, so the pieces lost more mass than at 0.6 mol/dm³.
Why this answer loses marks
The stronger salt solution contained more salt.
That restates the condition but does not link the larger concentration difference to a steeper gradient, more water leaving and greater mass loss.