Osmosis - GCSE Science Required Practical

Osmosis Experiment with Potato Tissue

Introduction to Osmosis and Experimental Setup

• The experiment focuses on osmosis, specifically examining how different concentrations of solutions affect potato tissue.

• Three identical potato cylinders are prepared from the same potato to ensure consistency in results for comparison.

• The potato skin is removed as it is impermeable, which could interfere with the osmosis process being studied.

Measurement of Potato Cylinders

• Each cylinder is measured for length (approximately 30mm) and mass using a high-resolution balance accurate to two decimal places.

• The initial mass recorded for one cylinder is 2.92 grams, which will be crucial for later calculations.

Preparation of Solutions

• Distilled water is used as the first solution; 10 milliliters are accurately measured and labeled to avoid confusion during the experiment.

• Two additional solutions are prepared: 0.25 molar sucrose and 0.5 molar sucrose, representing varying sugar concentrations that will impact osmosis.

Conducting the Experiment

• Samples were allowed to sit overnight (24 hours), enhancing observable changes in mass and length due to osmosis.

Collecting Results After Osmosis

• After soaking in distilled water, the length of one potato cylinder increased to 32mm, indicating water absorption through osmosis.

• The mass after soaking in distilled water rose to 3.12 grams from an initial 2.92 grams, confirming an increase due to osmotic activity.

Observations with Sucrose Solutions

• In the 0.25 molar sucrose solution, there was minimal change in length (remained around 30mm), but a slight increase in mass was noted (3.06 grams).

• For the strongest solution (0.5 molar sucrose), no significant change in length was observed; however, mass decreased from 2.87 grams to 2.62 grams, indicating loss of water via osmosis.

Data Analysis and Calculations

• Differences in both mass and length need calculation by subtracting initial measurements from final ones post-experimentation.

• Percentage change calculations are introduced: [(final mass - initial mass)/initial mass times 100] helps quantify changes effectively across samples.

Graphical Representation of Results

• A graph illustrating expected trends shows that as sugar concentration increases, potato tissue gains less weight until reaching a point where it may lose weight due to higher solute concentration outside cells.