Edible Science With Ice And Salt

hands-on experiment salt and ice heat transfer

Here’s how you can make a tasty sorbet in five minutes while learning about the effect of freezing point depression with ice and salt.

C(9) found the experiment in our Science Experiments book. We had all the supplies so we were ready for some spontaneous learning fun!

hands-on experiment salt and ice heat transfer

What You Need

  • Orange juice (or other juice)
  • Crushed ice (or snow)
  • Salt (about 4 tablespoons)
  • 2 ziplock bags, one larger than the other
  • warm gloves

What You Do

1. Pour orange juice into the smaller ziplock bag.  Squeeze out excess air and seal.

hands-on experiment salt and ice heat transfer
2. Place the bag inside the larger ziplock bag.
3. Fill the larger bag with crushed ice so that it surrounds the orange juice bag.
hands on experiment with ice and salt
4. Add salt to the ice. The book suggests 4 tbsp but we just sprinkled liberally.
hands-on experiment salt and ice heat transfer
5. Squeeze out excess air and seal the large bag containing everything.
6. Gently massage the bag so that the salty ice is constantly coming into contact with the orange juice bag.
hands-on experiment salt and ice heat transfer
7. Continue squishing for 5-10 minutes, observing the changes in how the orange juice looks and feels.
hands-on experiment salt and ice heat transfer
ice and salt experiment

What Happens

The orange juice gradually solidifies and turns into sorbet!

hands-on experiment salt and ice heat transfer

The Scientific Explanation

Adding an impurity (salt) to ice lowers its freezing point. The ice wants to melt back to water, but to do this it needs to absorb heat from somewhere – in this case, the orange juice. Heat is transferred from the orange juice to the ice, freezing the orange juice.

This is an endothermic process (heat is absorbed).

For a detailed molecular explanation of why salt melts ice, see this article.

What We Might Try Next Time

We ended up with a very healthy snack, but for a treat we might make a sweeter sorbet by adding sugar. (Here are the ingredients for a simple lemon sorbet, and a whole list of delicious sorbets here – courgette (zucchini) sorbet looks interesting!)  We might even try making ice cream in a bag.

hands-on experiment salt and ice heat transfer

Further Resources

Why Does Salt Melt Ice?

An “Ice Energy” lesson plan (includes ice cream recipes)

Science Experiments: Loads of Explosively Fun Experiments You Can Do

Science Experiments Robert Winston

 

For more hands-on learning fun, head over to Hobbies & Handicrafts  at Highhill Homeschool, Homeschool Review at Hammock Tracks, and Science Sunday at Adventures in Mommydom.

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18 thoughts on “Edible Science With Ice And Salt

  1. We’ve made ice-cream in a bag before – it’s a bit soft but very tasty. And it’s an interesting process to watch. The children love it – what’s not to love with food involved! I love how you write your science posts- very methodical!!

    1. Thank you! With the low gluten and sugar diet around here, taste standards are pretty low – I’m sure tasty soft ice cream will go down VERY well! 😀

  2. Love this experiment, and your clear instructions! I’m bookmarking this yet again. 🙂 Experiments that involve food are my favourite type of learning. 🙂 Thank you for sharing.

    1. Thanks for the pin, Ticia. I nearly listed the gloves as optional, but after reading about the science of this (how cold it gets) I realised that to give the mixture a proper squishing you really need them if you’re going to avoid frostbite!

  3. Hi,
    I got so into reading your post I forgot how I found you. Then I went back to my email and realized that you posted a comment on a blog I write for Family and Faith Matters – about the dinner conversation book.
    Great posts – so interesting I want to come and be in your classroom.
    Many blessings,
    Janis http://www.janiscox.com Author of Tadeo Turtle
    I also blog at Under the Cover of Prayer.

    1. Ooh yes ice cream snow is on my list too! I’ll have to look up ice cream in an ice cream ball – did you post about it? Thanks for stopping by, Jessy. 🙂
      Lucinda

  4. My son has been freezing everything and calling it his desert. Frozen banana in the peel, a cup of lemon juice and water, tomato……. With this experiment he could watch things freeze. Thanks for linking with Hobbies and Handicrafts.

    1. Sounds like great edible science! My daughter’s favourite is frozen goats’ milk. Doesn’t appeal one bit to me but she insists it’s delicious!

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