Summary: A sure favourite for all ages: a quick and easy recipe for making ice cream in a plastic bag!
Set-up: 5 mins
Play: 30 mins
- 300ml cream
- 2 tbsp caster sugar
- 1 tsp vanilla essence
- 2 trays of ice cubes
- 6 tbsp rock salt
- 1 medium ziplock bag
- 1 large ziplock bag
- Tea towel or oven gloves
What to do
Have your child help you measure out the cream, sugar and vanilla and place them into the medium sized ziplock bag. Zip up the bag: how can you mix the ingredients without opening the bag? An opportunity for squishing and squeezing!
Place the ice into the larger ziplock bag, and spoon the salt on top. Place the medium bag inside the lager one and zip up the bag. Explain that for the next five to ten minutes you need to keep mixing the ingredients, through the larger bag. Massage and shake the bag until the mixture becomes the consistency of ice cream. Talk about the changes that you see – to both the mixture and the ice in the bag. The bag will make your child’s hands really cold, so they might like to wear oven gloves or wrap a tea towel around the bag. Also watch out for drips from the larger bag as the ice begins to melt.
Once ready, remove the ice cream bag from the larger one and rinse off the excess salt. Snip a hole in the corner and squeeze the ice cream into a bowl or cone, or simply eat it from the bag with a spoon!
Ask your child how you could make ice cream in different flavours / colours, and try out their ideas.
Try the experiment again, without adding salt. What happens to the ingredients over time now? How do the ice cubes look different this time? In this experiment, the salt lowers the freezing point of the ice, which means the ice cream freezes more quickly. You will notice the ice with salt added starts to melt while the ice cream freezes. Without salt added to the ice, the ice cream mixture won’t get cold enough, and won’t become ice cream.
What happens if you try other kinds of salt, such as table salt?
What learning does this activity promote?
Measuring and counting, perseverance, curiosity, experimentation
By Dr Vicki Hargraves