Rediscovered Families

How To Make Ice Cream In A Bag (A Delicious STEM Activity)

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DIY ice cream in a bag is fun STEM activity for kids that ends with a yummy treat! Click through to get our easy recipe and learn about the science behind this homemade ice cream.

ice cream in a bowl

I remember it like it was yesterday.

I arrived at the school to see my  son jumping around the playground. He held tight to his plastic bag and wore a massive grin. He spotted me and waved wildly. “Mo-m! Lo-ok! ICE CREAM!” The enthusiasm was infectious. All around his classmates hopped, jumped and bounced with their bags. It was the first day of Kindergarten and the class was making ice cream in a bag. I came to join in the fun. 20 bouncy kids burning off a ton of energy and learning that science is cool!

There was no doubt about it, these teachers were brilliant. And this was an activity worth doing, because kids loved it.

Have you ever tried making ice-cream in a bag? It is a super fun activity. Kids love it of course. The process seems magical and it never fails to impress. As a side bonus, it gets them outside and bouncing and that is always a great thing.

Want to know the best part? It is also a fantastic science experiment. But more about that later. Scroll to the bottom of the post if you want to understand the science behind making ice cream.

Let me show you how to make this ice cream treat. It is easy and only needs a few ingredients.

How to make ice cream in a bag

HOW TO MAKE ICE CREAM IN A BAG

YOU WILL NEED:

(Makes 1 serving)

  • 1 cup half and half
  • 1 teaspoon vanilla extract
  • 2 tablespoons sugar
  • A quart size zip top bag
  • A Gallon Size zip top bag
  • ½ cup rock salt
  • Ice
  • Mittens or towel
Mom Tip: Personally, I would consider using brand name bags for this activity. I have found the brand name bags to be more robust. The bags are going to be manhandled and you really don’t want anything to split open.

INSTRUCTIONS:

adding vanilla to the cream

  1. In a quart size zip-top bag, combine half and half, vanilla, and sugar. Push out excess air and seal.
  2. Fill a gallon size zip-top bag halfway full of ice. Add the rock salt. Place the quart size bag inside and seal the top.

preparing the ice

  1. Shake for 10 to 15 minutes, until the ice cream has set up and thickened. Pour into to small bowls and enjoy!

summer STEM

  1. Remove the ice cream-filled bag from the ice and wipe the bag clean of salt.
  2. Enjoy your creation right out of the bag or serve it in bowls with sprinkles.

homemade ice cream

Store any leftovers – what are the chances?? – in a freezer.

ADAPTATIONS

Start planning for your next batch and consider making new flavors, too. Maybe this is how Ben and Jerry got started

Related: 26 Fun Frozen Treats Your Kids Will Love

GO WASTE FREE

If you are trying to reduce your use of plastic bags, try this version. It uses coffee cans instead of bags.

TIPS FOR MAKING ICE CREAM IN A BAG

A word of caution, the bag will get very cold once you add the salt to the ice. Mittens will protect tender hands. Wrap the bag in a towel if your mittens are packed away for the summer.

And remember, this ice cream is very soft and melts quickly. So, it is best eaten out of a bag or a bowl. An ice cream cone would get drippy very fast.

A QUICK EXPLANATION OF THE SCIENCE

This is the part where we learn about the science. Making ice cream in a bag helps you explore a bunch of scientific principals like

  • Phases of matter
  • Freezing and freezing points
  • Food chemistry
  • Laws of thermodynamics

QUESTIONS TO ASK

We can ask ourselves some questions

  • What changes do we see in the ingredients change during this process?
  • How does the ice change?
  • How does the bag feels after adding the salt?
  • What transforms the liquid ingredients into frozen ice cream?

WHY THE ICE CREAM FORMS IN THE BAG

Let’s look at the science in detail. Ice absorbs energy as it melts. As it does the water changes from a solid to a liquid.  In this experiment the ice absorbs the energy from the ingredients of the ice cream. It also absorbs energy from the outside environment (like your hands). This energy transfer cools the ingredients and makes the bag feel cold.

In physics, the second law of thermodynamics tells us that heat always moves from an object at a higher temperature to an object at a lower temperature. The refrigerated ingredients for the ice cream may be cool, but they are still warmer than the ice. So the heat is going to flow from the ingredients to the ice.

Salt lowers the freezing point of the ice. When you add salt to the ice, more energy is needed to melt it. Therefore, more energy is absorbed from the ingredients. This cools them enough to freeze them into a solid. Which happily creates the yummy end product of ice cream.

The shaking moves the warmer ingredients from the inside to the outside of the bag, so everything freezes evenly. It also adds air to the final product and creates the texture of ice cream. Yum!

Are you ready to try this yummy experiment with your kids? It’s a fun activity and may earn you the title of the coolest parent in the neighborhood. You’ll also be creating memories that will last a lifetime. Trust me. You’ll be glad you did.

How to make ice cream in a bag

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