Ice Cream Science
On Tuesday I had about 14 children and a selection of adults and a baby at my house making ice cream. We have between bought into a science scheme called UPD8. There are different themed units and lots of activities, powerpoint presentations and worksheets.
We used the powerpoint presentations to look at some of the science behind why you need to quick freeze ice cream. Did a challenge with lego to demonstrate that the longer it takes to freeze water the bigger the ice crystals. We looked at the effects on temperature of adding salt to water. We tasted fresh ice cream and ice cream which had been melted and refrozen and compared the differences.
Then we made the ice cream 
Smashing the ice took sometime and was very cold and wet and messy!
It was very slightly organised chaos as lots of people started measuring out sugar, cream and milk. We did it in two groups plus I’d sent Jonathan and Samuel off to play and agreed to do the ice cream making with them much later.
We had a go at doing soya ice cream too for the vegans among us – it worked very very well.
More measuring of milk with the second group.
I’ve even got a white board now – very strange! Spot the deliberate mistake in the recording of temperatures – who was that who wrote that down, hope it wasn’t one of my maths group! We couldn’t do the whole experiment with different amounts of salt in the ice as the thermometer only went down to -10. Talked about fair testing too
The older children made the ice cream with different degrees of success - I think we didn’t carry on with cooling it for long enough as many of them didn’t freeze properly. The Soya ones were amongst the first to be made and froze the best – we think this is because they were going for longest rather than being made from soya. We had used this method but had also left some of the packets of ice cream to set without agitating them. This was to see if there was a difference between these and the aggitated ones (which should have frozen more quickly) but we didn’t have much actual solid ice cream. However the soya version had an agitated and a non-agitated one. The non-agitated one did taste more grainy – which was great as this is what should have happened. Slower freezing should give bigger crystals which should therefore taste more grainy, quick freezing is the way to get smoother ice cream.
With the bigger kids out of the way I was left with only Jonathan and Samuel. It is amazing how much easier it is to do the experiment with 2 children rather than about 14. I even managed to take more photos as we went along.
Here are the ingredients and other bits and bobs we needed.
100ml cream
100ml milk
50 ml sugar
bit of vanilla essesnce
3 cups ice
1 cup salt
2 bags
a towel
lots of vigorous shaking.
Mixing the sugar into the cream and milk, in some of the ones we had made earlier they had stayed separate so we attempted to dissolve the sugar a bit more this time.
50 ml sugar waiting to be poured into the bag.
Getting 3 cups of ice was cold work.
Jonathan is still mixing his around while Samuel has a taste – I don’t think we mixed for long enough as his was still very runny.
I wish I had had the time to try this out beforehand as I think I could have had a better idea of how long to keep agitating it for and when to tell them to stop it as it wouldn’t freeze any-more. We had some problems with salt leaking into the ice cream bags so some ice cream was very very salty. Over all it was a great session, lots of fun, quite yummy and there was even some science involved. I think one of the mums thought the most interesting bit was watching a clip of Heston Blumenthal with hair!
