1. National 5 Biology
Diffusion and Osmosis

2. We are learning to Describe osmosis in relation to practical examples
Relate what we learn through the experiments to osmosis in animal cells

3. Osmosis Lab
You are going to set up 4 different experiments between you
Follow your instructions carefully your group members depend on you to do things properly

4. Experiment 1 Vanilla or peppermint in a balloon
Using a dropper place two drops of vanilla or peppermint inside a deflated balloon without getting any on the outside.
Inflate the balloon slightly and place inside a bag and not the end
Leave for 20minutes

5. Experiment 2 Collect two boiling tubes Place distilled water in tube 1
Place salty water in tube 2
Cut two cylinders of potato using cork borers take note of their appearance and their weight
Place one cylinder into each boiling tube
Leave for 30minutes

6. Experiment 3
You have three beakers in front of you each with different solutions and an egg with the shell removed
Try to decide what type of solution you have in each beaker based on the following:
Hypertonic – has less water than the cells
Isotonic – has the same concentration of water as the cells
Hypotonic – has more water than the cells
Remember water moves from a high water concentration to low water concentration

7. Experiment 4 Observe the information about the sultanas
Using the following words define what state the cells are in
Plasmolysed – vacuole has shrunk and cytoplasm and membrane have shrunk away from the cell wall
Turgid – vacuole is swollen pushing cytoplasm and cell membrane against the cell wall
In each case state if water has moved into the cells or out of the cells

8. Round Robin
Share all the information from your experiment with your group
Each person takes a turn and no one interrupts whilst they speak - 2minutes each
Once finished you can ask questions about what they did and what they found out

9. Place mat You have been given a large piece of paper
Draw out the placemat as follows
Each member of the group has two minutes to write down the important points raised in the experiments
Now as a group decide what the main points should be and write them in the centre

10. Conclusions
Water moves by osmosis from a high water concentration to a low water concentration
If a solution is hypertonic to the cells then the cells will lose water and become plasmolysed
If a solution is isotonic to the cells then the cells will remain unchanged
If a solution is hypotonic to the cells then the cells will gain water and become turgid

11. Osmosis in plant cells
The vacuole has shrunk and cytoplasm has come away from cell wall due to loss of water
No change to cell due to equal water concentrations
Vacuole has become swollen and pushes the cell contents against the cell wall

12. Osmosis in animal cells
Cells have shrunk due to loss of water
No change to cells – concentration of water is equal
Cells have swollen and burst due to gain of water - why?