Freezing Chemistry: Ice Cream in a Bag
Hosted by: UT Austin Chemical Engineering Graduate Leadership Council
Visit our Booth: Sunday, February 28, 2021, 12 p.m. - 4 p.m.
Recommended Grades: K-5
- Measuring spoons and cups
- Half-and-half, milk, or heavy whipping cream
- Vanilla extract
- Ice cubes
- pint-sized or sandwich-sized sealable bags
- Gallon-sized sealable bags
- Small towel or oven mitts
- In 2 small sealable bags, place one tablespoon of sugar, ½ cup of half-and-half (or milk or milk alternative or heavy whipping cream), and ¼ teaspoon of vanilla extract. Seal both bags well. Feel and observe the bags. Write down your observations.
- Add 3-4 cups of ice to 2 gallon-sized bags. Pour 1/2 cup of salt into one of the bags of ice. What do you think the ice will do?
- Place one of the bags of ingredients into the bag with ice and salt and the other into the bay with just ice. Seal the large bags tightly.
- Wrap each bag in a towel and shake for 5 min. Every few minutes check on your ingredients. Write down what you observe, what you feel and see. Are your ingredients still liquid? Is there a difference between the bag with salt and the bag without? What does the ice look like? How cold does each bag feel?
- After shaking each bag for 5 min, take out the ingredient bags from the ice. Did you make ice cream? What are their differences? Why might there be differences between each bag? Write down your observations.
- Enjoy your treat!
In order to make your homemade ice cream, your ingredients need to get very cold and actually freeze. Instead of placing the ingredients for ice cream in the freezer, you mix together salt and ice to make a solution.
Adding salt to the ice lowers the temperature at which water freezes. You will actually notice your ice melting as your ice cream ingredients start to freeze. With just ice, the temperature is not low enough to freeze the milk. When icy roads are salted in the winter, the same thing happens. The salt lowers the freezing point of water and causes the ice to melt, making it safer for you to drive.
Shaking the bag allows the warm cream mixture to move around to allow for better freezing. Plus it also creates a little air that makes the ice cream a bit fluffier.
Is ice cream a liquid or a solid? Homemade ice cream changes states of matter. Also more chemistry! It starts out as a liquid but changes to a solid in its frozen form, but it can go back to a liquid when it melts. This is a good example of reversible change as it’s not permanent.
For a more in-depth explanation, click watch the Science Buddies video below.
The UT Chemical Engineering Graduate Leadership Council is always looking for opportunities to serve our community. If you are interested in partnering with the GLC on an outreach event, please reach out to our president Sean at firstname.lastname@example.org.
The UT Chemical Engineering Graduate Leadership Council is responsible for the management of professional enrichment, service, social, financial, and recruitment activities as it pertains to chemical engineering graduate students at UT.