Background:

Ice has to absorb energy to melt. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the bag of ice!). When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes. Ideally, you would make your ice cream using sea salt instead of the small crystals you see in table salt. The larger crystals take more time to dissolve in the water around the ice, which allows for even cooling of the ice cream.

  • Measuring jug
  • 125ml milk
  • 125ml whipping cream (heavy cream)
  • 50g sugar
  • 1/4 teaspoon vanilla
    essence
  • 75g salt
  • Approx. 750ml of ice.
  • Large ziplock bag
  • Small zip lock bag
  • Washing up bowl
  • Kitchen scales
  • Spoon, bowl and
    toppings (if you wish).
  1. Place the small zip lock bag into a bowl on the scales
    and tare the balance (set) to 0.00g.
  2. Add 50g sugar, 125ml cream and 125ml milk into the
    small bag.
  3. Seal the bag.
  4. In the larger bag place the ice.
  5. Measure 75g of salt and place into the large bag
    containing the ice.
  6. Place the sealed small bag inside the larger bag
    containing ice and salt then seal the larger bag.
  7. Over a washing up bowl. Gently rock the large bag from
    side to side (hold it by the top seal / use gloves so you do
    not damage your hands).
  8. Rock for 20-25 mins or until the contents have solidified
    into ice cream.
  9. Once the ice cream has solidified, open the large bag,
    remove the smaller bag, open and serve the contents.
  10. Add toppings (if you wish) and enjoy!
  11. The ice can be placed in the sink to melt, do not touch
    the ice with your bare hands.
  1.  Try to make different flavour ice cream. Which flavour tastes the best?
  2.  Can you add fruit? Does anything happen to the texture or the ability of the ice cream to
    freeze by adding fruit?
  3. Does the type of fruit change the texture of the ice cream?

What makes the best flavour ice cream?

Tweet or email your ultimate ice cream recipe, conclusions or your findings to:
#chemistry4all #LJMU_CfA #icecream4all  chemistryforall@ljmu.ac.uk

Click here to download PDF version of making ice cream