The girls love all things science at the moment and this is a great experiment you can set up in three minutes with just four things. I showed the girls how to run a proper science experiment, we made predictions and saw a fascinating chemical reaction which we had to repeat four or five times as it was so much fun.
What you will need…
- Washing up liquid (we used Fairy Liquid and we poured a little into a small bowl but I would use an egg cup next time as you don’t need much)
- Milk (we used semi-skimmed but it would be interesting to test different milks)
- Cotton Buds
- Food colours or liquid water colours
A big part of the fun of this experiment is setting the scene. I made a fuss about setting up a professional science experiment and talked about making predictions and following the steps carefully. The girls loved this as they felt like ‘proper grown up scientists’.
Post the mad scientist routine we simply poured about 2-3cm of milk into a wide shallow bowl. The cow milk jug and goggles are not necessary but they are fun! (the coke in the background was for our next experiment – the exploding mentos one which we tried on the same night – but it didn’t work!).
Then drop in whatever colours you have – four or five drops dotted in is a good start. (If you put them close together in the centre you will get a more focused firework effect. Space them out and you will have mini fireworks around your bowl. We liked it both ways.) Check out the mixture with a magnifying glass if you like and discuss shapes and colours. Introduce words such as viscosity if you want to get technical!
The key thing at this stage is to ask the children to make ‘predictions’ – i.e. what do you think will happen? This was a new word for them and we talked about what it meant. I asked them what they thought would happen if they put their fingers in. We made the prediction then tried it. We talked about the results. We then went on to make another prediction. What would happen if we put a cotton bud in without the soap? We did it and looked at the results. I have to say the girls were looking at me with ‘what is the point of this eyes’ at that moment. But I think this only heightens the wow factor for the next bit! Then make your next prediction – what will happen if you dip soap into the bowl? Pop the cotton bud into the washing up liquid and dip it into the centre of one of your colours (if you have spread them out) or the centre of the bowl if you have grouped them together.
You can see the reaction on the left in Grace’s bowl – the colours dart away from the cotton bud. The colours continue to swirl without the cotton bud being present until the soap is distributed evenly and it stops moving. It is such fun to watch. Don’t forget to dip the cotton bud in and out to continue the reaction.
A great explanation for this can be found here at Steve Spanger science. However my girls are small so this is what I said….. Milk is mostly made up of water but it also contains vitamin, mineral, protein and fat molecules (they are smaller than the eye can see but they look a bit like water beads). The fat molecules are suspended in the milk. Suspended means ‘hanging about’! Washing up liquid is a chemical and it weakens all the bonds that hold all the little beads/molecules together in the milk. A bit of the washing up liquid really likes the fat molecules in the milk and tries to chase them around the bowl and hold their hands. So all the colours in the water, which don’t contain fat molecules, get pushed around the bowl and that is how they move and you get the fireworks effect.
I don’t know how much they understood – probably because I am not a scientist and it is hard to explain. Honestly, as you scientists out there will know, I probably missed some really important bits out! But on a basic level we talked about interesting scientific words such as ‘predictions’ and ‘molecules’. Hopefully when they meet these words at school they will remember this experiment and it will prove useful to them! Plus we had a really fun 20 minutes!
Enid Blyton rating: 7 out of 10 (A quick, fun activity that you can pull out when you have a spare 10-15 minutes. No pressure to talk about the science stuff either – you could just have fun with it and wait for the children to ask you questions.)