About Lesson
Experiments on Osmosis
1. Demonstrate Osmosis using a Visking tubing
The set-up was left for 30 minutes.
Observation
- The visking tubing swell/increased in volume.
Explanation
- The sucrose solution in visking tubing is hypertonic; while the distilled water is hypotonic; Water molecules moved from distilled water to the visking tubing by osmosis;
2. Demonstrate Osmosis using a Potato cup
Observation
- The potato cup will be filled with solution;
Explanation
- Sugar crystals dissolved in moisture from the cells in the cavity forming a strong sugar solution. The sugar solution was hypertonic to the cells in contact hence water was drawn from the cells into the sugar solution by osmosis. In turn, the cell’s sap became hypertonic to adjacent inner cells hence drew water from them by osmosis.
- This successively continues from cell to cell until water is drawn from the water (hypotonic solution) in the Petri – dish. A continuous movement of water from the Petri – dish, through the cells and into the potato cavity is created. Resulting to increase in sugar solution in the cavity and a drop of water level in the Petri – dish.
Control Experiment
- Using a boiled potato instead of a living one. There would be no observable change. Boiling denatures the cell membrane hence stop
3. Demonstrate Osmosis using a thistle funnel and Visking tubing
Observation
- The level of sucrose solution rises;
Explanation
- Water molecules move from distilled water, which is hypotonic; into the sucrose solution that is hypertonic; across the semi-permeable membrane by osmosis; hence the sucrose solution rises.