We have been learning about freezing point and how salt lowers the freezing point of water, at the same time making the ice colder. Students connected this with making homemade ice cream, and I opened my BIG MOUTH and mentioned that they didn't need an ice cream maker. "You can just make it in bags at home. It's really easy, and it tastes SO GOOD!" How can you say no after that? I did assure them that this would be a lab, not just an "activity."
I gave them a lab sheet that looks like this:
Ice Cream LAB
Name _____________________________
Purpose: To see if salt will lower the temperature of ice enough to freeze the milk solution into ice cream.
Hypothesis: If I ____________________, then ________________________.
Procedure:
- Pour 1 cup of milk into a ziploc bag.
- Pour 2 tsp (or more to taste) in the same bag.
- Pour a dropper of vanilla into the same bag.
- Seal the bag after removing all of the air.
- Write your name on a gallon size freezer bag.
- Pour one scoop (about 2 cups) of ice into the large bag.
- Pour two hands full of rock salt onto the ice into the large bag.
- Place the small bag into the large bag, making sure it is covered with the ice and salt.
- Wrap the bag in a towel.
- SHAKE! SHAKE! SHAKE! (Continue shaking for about 5 minutes, or until mixture is a solid.)
- Cut the corner of the small bag and pour ice cream into a cup or bowl.
Conclusion:
(Yes, the materials would have cost a small fortune so students very kindly brought in all of the supplies.)
Making ice cream requires a lot of shaking...
...and a lot of mixing.
Overall, it was great, the kids had fun, and I think they understood why we were making the ice cream.
I asked them at least 100 times.
(I also did this at home with my 5-yr-old. He LOVED it and now thinks I make the "best ice cream in the world.")
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