Original application practice · 14 indicative marks

Osmosis: from mass change to evidence

Answer without the guided prompts, then review the science and working.

These are our practice questions and indicative marks, not examination-board questions or an awarded grade. The data are shared with guided practice; a case you have already studied is not an unseen test.

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⁻³Initial mean mass / gFinal mean mass / g
02.002.18
0.22.002.06
0.42.001.94
0.62.001.80
0.82.001.68

Five exam-condition questions

1. Calculate the percentage mass change at 0.4 mol dm⁻³.

2 indicative marks

2. Describe the effect of sucrose concentration on mean mass change.

3 indicative marks

3. Explain the mass change at 0.8 mol dm⁻³.

3 indicative marks

4. Estimate the concentration at which there would be no net mass change.

2 indicative marks

5. A student concludes that every cell contains exactly 0.30 mol dm⁻³ sucrose. Evaluate this conclusion.

4 indicative marks

Print exam-condition questions · Print questions and guidance

Selected OCR A H420 connections: 2.1.5. Use official papers for examination-board assessment.