Last term, students in the Science Workshop experimented with the effect of sodium chloride (NaCl) – aka rock salt – on cooling ice. Students learnt that by adding rock salt to ice, the mixture becomes significantly colder than just pure ice water. While pure water freezes at 0 degrees Celsius, water mixed with salt will freeze below 0 degrees Celsius. This experiment was conducted in (some may say) the best way possible – through making ice-cream!
By adding a mix of delicious ingredients together in a bag (see resource list below), and using a simple salt/ice mixture to create a freezer like effect around the bag, students were able to finish off their term with a mouth-watering treat. Hopefully learning some “cool” science in the process!
Ice-cream in a bag experiment
- Measuring spoons and cups
- Vanilla extract
- Ice cubes
- Small, sealable bags
- Large sealable bags
- In each small sealable bag, place one tablespoon of sugar, ½ cup of half-and-half (or milk or heavy whipping cream), and ¼ teaspoon of vanilla extract. Seal both bags well.
- Add four cups of ice cubes to one of the large, gallon-sized bags. Then add ½ cup of salt to the bag.
- Put one of the small bags you prepared into the large bag with the ice cubes. Be sure both bags are sealed shut.
- Put on oven mitts or wrap the bag in a small towel and then shake the bag for at least five minutes. Feel the smaller bag every couple of minutes while you shake it, and take a peek at it.
- Now do it again, this time with NO salt. What is the difference?
Experiment sourced from: https://www.sciencebuddies.org/stem-activities/ice-cream-bag