Demonstration to show convection in class

[lcg]

I have to do a demonstration to show convection in class.
I was wondering what could be a simple experiment to set up in which I could show that convection exists. I've had a few ideas and am wondering if you could come up with any. :shy:
Thanks,
lcg

 

[Adrian Baker]

The std one is potassium permanganate (or whatever its new name is) crystals dropped through a glass tube into the edge of a big beaker of water.
Put your finger on the end of the tube, remove the coloured water in the tube and discard this.
Then, heat the 'corner' of the beaker where the crystals are and watch the dissolving crystals set up beautiful convection currents.

Or how about the old mine ventilation one?

 

[lcg]

I'll try your suggestion. I'm not sure whether I can use school equipment that's why it's got to be simple but I think I have some potassium permanganate crystals somewhere here. I'll check and explore your suggestion.
Thanks.

 

[Sarahchichi]

You can also demonstrate convection by this simple experiment I suggest here. Firstly, get a beaker with medium size. Then, separate the beaker into halves by a white paper/cardboard, but leaving some space at the bottom of beaker to allow the flow of air. Thirdly, put a light candle at one side of the beaker. Afterwards, light a smoking paper and point it at the other side of the beaker. As a result, you can see the flow of smoke down to beaker and then up to the candle side. This flow of smoke indicates the convection of air

 

[jdavel]

Icg,

This probably wouldn't demonstrate convection as obviously as the previous two, but in a pinch (and with some explanation from you) it might work. Jjust have each of two people in your audience hold their had twelve inches from a candle flame, one straight above and one to the side of the flame. The fact that the hand above the flame gets hot faster can only be accounted for with convection. Can you explain why?