Practical 6
Modelling Diffusion
Equipment (per group):
- 2 Petri dishes (one containing solid agar)
- Tweezers
- Stop-clock
Chemicals:
- 2 crystals of solid potassium permanganate (KMnO4)
- Water
Safety
These safety points mainly tell you about hazard. You will need to think about the risk(s) this might pose, and how you can minimize the risk.
- Potassium permanganate can irritate the skin and eyes. Wear safety glasses and protective gloves.
Method
- Take the Petri dish containing agar, and use the tweezers to place a crystal of Potassium permanganate in the centre. Put on the lid, ensuring that the dish remains level.
- Carefully fill the other other Petri dish with water, and position in a safe place. Use the tweezers to place a crystal of Potassium permanganate in the centre, taking care to avoid moving the dish.
- Start the stop-clock. Observe what happens in each dish after 1, 5,10, 20, 30 minutes.
Results
| Time (minutes) |
Observation |
| 1 | |
| 5 | |
| 10 | |
| 20 | |
| 30 | |
Discussion
- Explain what has happened to particles of potassium permanganate in each of the two Petri dishes.
- Was there a difference between the two dishes? If so, why might this be?