Ice-cream in a bag

Here’s another Kitchen Science experiment – ice cream in a bag. You can easily get ingredients needed for this activity and with easy steps that kids can do it without making a mess (just make sure the ziplock bags are tightly sealed! and double ziplocked if you’re really worried). It’s also quick so kids won’t get impatient with it. The best part? It’s yummy and you can create your own flavour!

Ingredients:
-1/2 cup heavy cream (whipping cream)
– 1/2 cup milk
– 1/4 cup sugar
– 1/4 teaspoon vanilla extract
– 6 tablespoons salt
– ice cubes, enough to half-fill a large plastic container. (crushed ice preferred over ice cubes as it has larger surface area)

Materials:
– Large plastic container
– 2 pcs large zipper-lock bags
– Towel or mittens

Steps:
1. Add heavy cream, milk , sugar and vanilla in a container. Stir well.
2. Transfer the content into a zipper-lock bag.
3. Seal the zipper-lock bag tightly.
4. Place it into the other zipper-lock bag. Seal it tightly.
5. Add crushed ice into the large plastic container until it’s half filled.
6. Add 6 tablespoons rock salt.
7. Place the zipper-lock bag in the container. Seal it.
8. Shake and roll it for 10-15 minutes.

 

Science notes
Possible science topics that you can explore with your child through this activity are state of matter and changes in state. Below are possible questions you can discuss with your child.

  • Is ice-cream a solid or liquid? Is it simply frozen ice-cream is solid and melted ice-cream a liquid? Frozen ice-cream is actually a mixture of different states of matter! This website by American Chemical Society explains the state of matter of ice cream for young children.
  • What is the change of state observed? Quite a few changes of state take place in this activity! Th obvious ones are change of state from liquid to solid (milk to ice crystals) in the first bag and change of state from solid to liquid in the plastic container. Probe your child to observe the water droplets in the second bag after the shaking and rolling as most might missed this. The bag is empty, so how do water vapour appear in the bag? This is another change of state, from gas to liquid.
  • Why is salt added to the ice? The dairy mixture need to be colder than ice to freeze. The salt added to ice lowers the melting point of ice. This makes the ice colder than it was before, to even below 0 degrees Celsius, hence increases the freezing rate of the diary mixture.

Extension

Another possible extension to explore this property of salt is to compare the freezing rate or melting of ice in normal water and in salt water.

Lastly, some videos to support your child’s learning in the topics mentioned above.

 

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