5 original questions · Application and evidence

Osmosis: from mass change to evidence

Use the context and data to draft a response, then compare your reasoning with an explanatory example.

Context and data

Comparable plant-tissue cylinders were immersed for the same interval in sucrose solutions at the same temperature. The table gives mean masses from three independent cylinders at each concentration. These original classroom data describe this tissue and method; no water-potential calibration is supplied.

Mean mass before and after immersion
Sucrose concentration / mol dm⁻³	Initial mean mass / g	Final mean mass / g
0	2.00	2.18
0.2	2.00	2.06
0.4	2.00	1.94
0.6	2.00	1.80
0.8	2.00	1.68

Original illustrative data. Use the stated assumptions and units; these are not examination-board questions.

This worksheet includes questions and data, with space for your responses. Answers are omitted.

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Five questions

1. Calculate the percentage mass change at 0.4 mol dm⁻³. Show the reference mass and interpret the sign.

2. Describe how mean mass change varies across the concentration range, using at least two numerical comparisons.

3. Suggest and explain why the tissue loses mass in the 0.8 mol dm⁻³ solution.

4. Estimate the sucrose concentration giving zero mean mass change by linear interpolation between the adjacent points. State a limit of the estimate.

5. A student claims that 0.30 mol dm⁻³ is the exact concentration of sucrose inside every cell. Evaluate this claim and suggest one useful improvement.