Cell BiologyRequired Practical

Required Practical: Investigating Osmosis

Part of Cell Transport — GCSE Biology

This required practical covers Required Practical: Investigating Osmosis within Cell Transport for GCSE Biology. Diffusion, osmosis, active transport, factors affecting transport, surface area to volume ratio, and practical investigations It is section 6 of 18 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.

Topic position

Section 6 of 18

Practice

18 questions

Recall

20 flashcards

🧪 Required Practical: Investigating Osmosis

Method - Effect of Salt Concentration on Potato Tissue

Prepare specimens: Cut potato into identical chips (same size and shape)
Initial measurement: Measure and record initial mass of each chip
Set up solutions: Place chips in different salt concentrations:
- 0% (distilled water)
- 0.2%, 0.4%, 0.6%, 0.8%, 1.0% salt solutions
Control variables: Same volume of solution, same temperature, same time period
Leave for 24 hours
Final measurement: Remove chips, pat dry carefully, re-weigh
Calculate: Percentage change in mass = (Final mass - Initial mass) ÷ Initial mass × 100

Expected Results and Explanation

Salt Concentration	Expected Result	Explanation
0% (distilled water)	Mass increase	Hypotonic - water enters by osmosis
0.2% - 0.4%	Small mass increase	Still hypotonic but less water movement
~0.5% (isotonic point)	No change in mass	Same concentration as potato cells
0.6% - 1.0%	Mass decrease	Hypertonic - water leaves by osmosis

🎯 How to Improve Accuracy

Use more potato chips for each concentration (larger sample size)
Repeat the experiment multiple times to identify anomalies
Control temperature throughout the experiment
Use more intermediate concentrations for detailed results
Pat chips dry more consistently to remove surface water
Use the same variety of potato
Measure mass to more decimal places

Practice Questions for Cell Transport

Which statement best describes diffusion?

A. The movement of particles from a region of low concentration to high concentration
B. The net movement of particles from a region of high concentration to low concentration
C. The movement of water molecules through a partially permeable membrane
D. The movement of particles using energy from respiration

1 markfoundation

Explain how osmosis causes a plant cell to become plasmolysed when placed in a concentrated sugar solution.

3 marksstandard

Quick Recall Flashcards

Define diffusion

The movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. No energy is required (passive process).

Define osmosis

The movement of water molecules from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration) through a semi-permeable membrane.