Core Practical: Investigating Osmosis

This lesson provides a detailed guide to the required practical on osmosis as required by the Edexcel GCSE Combined Science specification (1SC0). You need to be able to plan, carry out and evaluate this investigation, including identifying variables, recording results, calculating percentage change in mass and drawing conclusions.

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Aim

To investigate the effect of different concentrations of sucrose solution on the mass of potato cylinders, and to determine the concentration at which there is no net movement of water (the isotonic point).

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Apparatus

You will need the following equipment:

• Potato
• Cork borer (to cut uniform cylinders)
• Ruler (to measure cylinder length)
• Scalpel and cutting tile (to trim cylinders to equal length)
• Balance (accurate to at least 0.01 g)
• Paper towels (for blotting)
• 6 boiling tubes (or beakers)
• Boiling tube rack
• Sucrose solutions: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, 1.0 M
• Measuring cylinder (to measure solution volume)
• Labels or marker pen
• Timer / clock

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Method

Step-by-Step Procedure