What You'll Need
- 100mls Greek Yogurt
- 100mls Cream
- 6 Strawberries
- 3 ziplock freezer bags – small, medium and large
- tea towel
- oven gloves
How to Do It
- 1Mash the strawberries with a fork.
- 2Pour the yogurt and cream into a bowl together , stir on the strawberries. Mix it all together.
- 3Pour into the smallest freezer bag. Zip it closed.
- 4Put the small freezer bag inside the medium freezer bag and zip lock that.
- 5Put the ice and salt in the biggest freezer bag and sit the medium freezer bag into this. Zip lock it closed.
- 6Hold the big freezer bag with a tea towel for oven gloves and SHAKE, SHAKE, SHAKE for 10 minutes until the liquid turns to a frozen solid - ICE-CREAM.
Science Bites: How it Works
- The salt changes the melting point of the ice.
- A melting point is where a solid changes into a liquid. In a solid state – molecules are tightly packed.
- By adding salt to the ice it separates out into Na and Cl and this disrupts the ability of the ice to freeze.
- The more salt added the more effect it has on freezing and melting.
- Salt lowers the temperature at which water freezes ( this is called a freeze point
depression) so the salt ice will melt even when the temperature is below normal freezing.
- This change in melting point causes ice to take energy from the warm cream mixture and the environment. This energy melts the ice