First, we got a magnetic stirrer and set it on a fast setting. We put a magnetic flea in a beaker of water (800ml). Inside the magnetic stirrer, there is another magnetic and it creates a rotating magnetic field. This spins the flea which stirs the liquid and, if fast enough, will make a whirl pool. Using a magnetic stirrer is more efficient than other stirring devices when doing a fair test. Thanks to Barry Reid for donating it to us! Barry used to come to this school and is now the Senior Area Manager at Jencons, a global lab supply company.
When we had a whirl pool, we put red and blue food colouring into the whirl pool. The colours went through the bottom of the whirl pool and onto the flea and then slowly mixed in. We thought this could be a really good demo for open days etc. where people could design their own tornado/whirl pool with different food colouring and name it!