Science and homemade ice-cream

Free Science Experiments -

Science and homemade ice-cream

Almost every child I know loves ice-cream and for that matter most adults too. Lily and I are home alone together for several days these school holidays and it has been hot, hot, hot outside.

When I came across this quick and easy ice cream experiment and I thought it would be a great way to incorporate a love of ice cream with a love for science AND cool down.

So, grab your materials and explore the states of matter as well as freezing point of water in this yummy science experiment!

Materials

  • 2 sandwich ziplock bags
  • 2 freezer sized ziplock bags
  • ½ cup milk
  • ½ cup pouring cream (not double or whipped cream)
  • ¼ cup sugar
  • 1 tsp vanilla essence
  • Ice to fill half the freezer bag
  • ¾ cup salt (rock salt works best)

Method

Ingredients for a homemade ice-cream in a bag science experiment

  1. Put one freezer bag inside the other (this is to help stop leaks).
  2. Put the ice into the inner freezer bag.
  3. Pour the salt into the bag over the ice.
  4. Put one sandwich bag in the other (again to stop leaks).
  5. Add the milk, cream, sugar and vanilla into the sandwich bag and make sure you zip both bags securely so nothing leaks. 
  6. Place the sandwich bag inside the freezer bag and zip it up.
  7. Shake the bag for 10 -15 minutes. The longer you shake the firmer your ice cream will be. 
  8. Your ice-cream should come out like soft serve. 

Note: It's best to do this with 2 or 3 kids as they can share the shaking which gets very tiring. We actually put our bag on the trampoline for a while and made it bounce around which worked quite well except that the outer bag did break.

The Science

Explore states of matter and freezing points making ice-cream in a bag

Water can be in 3 states. Solid, liquid and gas. When water reaches 0ºC it goes from a liquid to a solid. This is because 0ºC is water’s freezing point. The cold temperature slows down the movement of the water molecules the point where they become so close together they form a solid. When salt (sodium chloride) is added to water it lowers it’s freezing point. The salt gets between the water molecules and stops them from being able to turn solid. The ice that is still solid is a lower temperature than it was before adding the salt. This super cold temperature surrounding the cream mixture helps it to reach it’s freezing point as well which is why is begins to firm up, hence the term ice cream.


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