Required Practical 02: Osmosis
About this practical...
This is a relatively simple practical that has much wider implications. You are going to find out the concentration of the solutions in plant cells. You need to take accurate measurements and plot a graph in order to discover the concentration of the unknown within the plant material. This teaches us other applications within scientific investigations.
Method:
1. Collect 5 boiling tubes and place them into the boiling tube rack.
2. Clearly label them with the appropriate solution (usually, 1.0, 0.75, 0.5 and 0.25 mol/dm3 sugar solution and a final one with distilled water.
3. Collect a potato (other vegetables may be used later) and carefully bore out your samples. Take care, the borers can be sharp.
4. Carefully measure the length and mass of each sample of potato and place it into the boiling tube. It is essential that you do not mix them up and record the lengths and masses accurately.
5. Place the boiling tubes into a water bath at 30° for 30 minutes. While waiting, complete your table and prepare for your graph.
6. After the time has elapsed, remove the potato cylinders, remeasure the length and after gently patting dry, find the new mass. (For consistency, it is essential that you treat each core the same way).
7. Calculate the percentage change in mass and length.
8. When you have plotted the graph, you will be able to work out the concentration within the cells of the potato.
Safety & Managing Risks
Usual lab rules must be followed: loose hair tied back, goggles worn throughout the lesson, bags and stools tucked away and notify the teacher of any spills or breakages immediately. Take care with the cutting/coring equipment, it is sharp. For more detailed information, please consult CLEAPSS.
Technician notes:
Boiling tubes (5 per pair)
Sugar solutions (1.0, 0.75, 0.5 and 0.25 mol/dm3)
Distilled water
Beaker large enough for 5 boiling tubes (water bath)
Thermometers
Borers and safety knife
Balances
Potatoes
This page was updated on: 8th January 2022