Ice Cream in a Bag

It’s been warm this summer and we’ve been enjoying a lot of ice-cream.  Instead of buying ice-cream, I thought it would be fun to make our own ice-cream.  With just a few ingredients, you can make ice-cream in a bag without the hefty cost of an ice-cream maker!  Plus, the kids are learning some science without even realizing it!

Here’s what you need to get started:

  • 1 tablespoon sugar
  • 1/2 cup milk, cream or half n’ half
  • 1/4 tsp Vanilla extract (or other flavoring – we tried peppermint too)
  • toppings – optional (we added mini chocolate chips)
  • 6 tablespoons salt (we used kosher salt)
  • 1 gallon sized Ziplock bag
  • 1 quart sized Ziplock bag
  • Enough ice to fill the gallon ziplock bag about halfway

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Add the salt and ice to the gallon sized ziplock bag.  Seal the bag and mix well.  Set aside.

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In the quart sized bag, add the sugar, milk, flavoring and toppings.  Mix and seal well.

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Add the bag with the cream mixture to the bag with ice and salt.  Seal the gallon bag and mix/shake well for at least 5 minutes. It will be very cold so use gloves or a towel if it gets uncomfortable.

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Open up the bag of ice and pull out your cream mixture.  It should have solidified a bit to a texture similar to ice-cream.  Open the bag, grab a spoon and enjoy! Yum!

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The Science behind the Activity:

When the salt is added to the ice, it lowers the freezing point of the ice so that the cream mixture can freeze quickly.  Water normally freezes at 32 degrees but by adding the salt you can lower the temperature as low as 2 degrees! This is the same reason why salt is added to icy roads to melt the ice so that it is safer to drive.  Plus, this is an opportunity to discuss how lowering the temperature of any liquid, not just water, can cause it to turn into a solid (soft solid in this case!)

Follow this link to see where I got the idea from and more details about the experiment: http://science.howstuffworks.com/innovation/edible-innovations/ice-cream3.htm

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