About Lesson
Practical activity: To demonstrate diffusion using potassium permanganate
Requirements
- A beaker
- Water
- Crystals of potassium permanganate
- Glass tube
Procedure:
- Drop a few crystals of potassium permanganate at the bottom of the beaker by putting them through a glass tube.
- Close the glass tube with your thumb.
- Half fill the beaker with clean water while still closing the glass tube.
- Gently remove the glass tube from the beaker containing water
- Observe over the next 15 minutes
Observation after 15 minutes
The potassium permanganate crystals dissolve and a purple colour spreads from the crystals at the bottom upwards. Eventually the colour is evenly distributed in the water.
Explanation
When potassium permanganate crystals dissolve, their molecules are free to move. The molecules are highly concentrated around the undissolved crystals and so they move to regions of low concentration. The molecules move along a diffusion gradient until they are evenly distributed.
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