Monday, February 2, 2009


With my grade 8s at school we're doing a unit on cells. Last weeks lesson was on osmosis and diffusion. The pictures below are of one of my demonstrations. Often topics can easily be simplified for the younger set. I did this experiment with Mason and Mickey at home and they loved it. Anything involving coloured water is surely a hit. Sure we didn't talk about cells and how the membrane behaves during osmosis but we did discuss how the plant drinks water and why the flower turned colour. They're now familiar with the big word "osmosis".

First get some white flowers. Carnations work nicely and they're cheap! Cut them to an appropriate length. The shorter the stem the faster the experiment will work.

Put water in each glass and add a significant amount of food colouring. Probably 5-10 drops. The more the better. Try to keep it the same for each glass. Try combining colours.

The flowers will need to sit for a few days. The tips will start to change first.

Here are a few of our successes. Variations:
- put the flower in one colour for a day or two and then switch to another colour for another day or two
- try more than two colours
- after it changes colour try putting it in clear water and see what happens

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