The Science Scoop: How to make ice cream in a bag (and learn while you do!)

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I’ve got a very tasty science experiment to do today!

Making ice cream in a bag is all science! This exciting experiment allows you to create your own frozen treat while delving into the world of freezing point depression, heat transfer, and the importance of agitation.

So skip the store and make your own delicious ice cream while talking about science!

How to make the Science Scoop homemade ice cream experiment

Supplies you will need

For this experiment, you’ll need:

For our lactose-intolerant friends: try using full-fat, canned coconut milk in place of the half and half. The fat content of the coconut milk should help it produce similar results.

Before you start

You can use a few variations of this experiment:

  • If you’re lactose-intolerant, try using full-fat coconut milk from the can
  • Chocolate ice cream is easy; just add cocoa powder
  • You can add toppings too, if you have them!


Here is how to do this experiment with your child:

Step 1: Make the ice cream bag

First, we are going to add the ingredients to the sealable sandwich bag.

Add 1 tablespoon of sugar, 1/2 cup of half and half, and 1/4 teaspoon of vanilla.

Seal the bag and place it to the side.

One tablespoon of sugar to the sandwich-sized bag
1/4 teaspoon of vanilla extract to the sandwich-sized bag
1/2 cup of 1/2 and 1/2 to the sandwich-sized bag

Step 2: Fill the gallon-sized bag

Add 4-5 cups of ice and about a 1/2 cup of salt to the gallon-sized bag.

1/2 cup of salt to the gallon-sized bag
5 cups of ice to the gallon-sized bag

Step 3: Place ice cream bag in gallon-sized bag and shake

Place the sealed sandwich-sized bag in the gallon-sized bag with ice and salt and seal it.

Place a towel over the bag and start shaking!

You will need to shake the bag for about 5-10 minutes. Every few minutes, feel the ice cream bag to see if the consistency has changed.

Step 4: Compare the results

After about a minute, take a look at the ice cream bag. What do you notice? Keep pausing to check out the ice cream bag to see how it changes over the next 5 minutes.

Step 5: Enjoy your science experiment!

What are you waiting for? Enjoy your ice cream!

You can add sprinkles or chocolate chips, place it in a cone, or even add some cocoa powder to make it chocolate ice cream.

Finished product!

The STEM behind the Science Scoop homemade ice cream experiment

This experiment teaches:

  • Freezing point depression
  • Heat transfer and air incorporation
  • Patience

How it works

Making ice cream in a bag is more than just a tasty treat – it’s science!

This experiment is a mix of freezing point depression, heat transfer, and air incorporation. The milk mixture gradually loses heat and transitions into a semi-frozen state. The sugar also helps lower the freezing point of the liquid slightly, which contributes to the overall freezing process.

When it’s done, you have a creamy ice cream in a bag!

Freezing point depression

This experiment demonstrates the principle of freezing point depression, which means it lowers the temperature at which the ice can exist as a solid.

Normally, water molecules arrange themselves in a specific way at 0°F, forming ice crystals. This arrangement doesn’t require much energy.

When you add salt to the ice, it dissolves into individual ions (sodium and chloride). These ions disrupt the orderly arrangement of water molecules, making it harder for them to form ice crystals.

Since water molecules struggle to form crystals in the presence of salt ions, they need to reach a lower temperature to achieve the same ordered structure. This is why the freezing point of the salt water is lower than that of pure water.

The more salt you add, the lower the freezing point and the faster the ice cream will freeze.

Utilizing the principle of freezing point depression occurs in other areas of life too, like preserving food or antifreeze in car radiators.

Cool, huh?

Heat transfer and air incorporation

As the ice in the outer bag melts, it absorbs heat from the inner bag containing the ice cream mixture. This transfer of heat is the driving force behind the freezing process.

The absorbed heat from the ice cream mixture causes its temperature to drop, initiating the formation of ice crystals and gradually transforming the liquid mixture into ice cream. The colder the ice bath (thanks to the salt), the faster this heat exchange occurs.

The second important piece here is the air incorporation, which occurs because we are shaking the bag. The small air pockets that are created from shaking the bag act like separators, preventing the formation of large ice crystals.


It takes several minutes to do this experiment, which will give your child a chance to practice patience (which is especially hard when it comes to ice cream!).

More experiments about food to try out with your child

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