July 23 is National Vanilla Ice Cream Day, and what better way to honor this timeless treat than by mixing up a little fun and science in your kitchen? Whether you're a parent, teacher, or lifelong learner, this "Ice Cream in a Bag" STEM activity is a fantastic way to cool down, learn something new, and enjoy a sweet reward.

Make Ice Cream in a Bag: A Tasty STEM Project

This hands-on science activity is suitable for both kids and adults. It utilizes simple household ingredients and teaches valuable STEM principles, such as freezing point depression and thermal energy transfer.

You’ll Need:

• 1 cup half-and-half or whole milk
• 2 tablespoons sugar
• ½ teaspoon vanilla extract
• Ice
• ⅓–½ cup salt (rock salt or table salt)
• 1 small zip-top bag
• 1 large zip-top bag
• A towel or gloves (for cold hands!)

Instructions:

1. Combine the milk, sugar, and vanilla in the small bag. Seal tightly.
2. Fill the large bag halfway with ice and salt.
3. Place the small bag inside the large one and seal the large bag tightly.
4. Shake for 5–10 minutes. (Tip: wrap in a towel so your hands don’t freeze!)
5. Enjoy your homemade vanilla ice cream!

The Science Behind the Scoop

Why does this work? It all comes down to freezing point depression. Salt lowers the freezing point of water, meaning the ice melts at a colder temperature than usual. This super-chilled mixture draws heat out of the milk mixture, causing it to freeze into ice cream. It’s a delicious way to observe phase changes, energy transfer, and chemistry in action—right at your kitchen table!

Learning Outcomes

This STEM activity reinforces:

• Scientific method
• Observation skills
• Chemical properties of salt and ice
• Real-world application of thermal energy

Why STEM Education Matters

At Harmony Public Schools-Central Texas, we believe learning should be hands-on, inquiry-driven, and deliciously engaging. Activities like this spark curiosity, develop critical thinking, and make science relatable for all ages.