#ScienceLessonAtHome of the day!
Julius Freezer!
This is a tasty way to demonstrate energy transfer during changes of state. It is also how the Ancient Romans made their ice cream!
#Homeschooling2020 #homeschool #HomeschoolinguK #Science
You will need:
✅ Two large, strong ziplock bags OR two plastic tubs with secure fitting lids, one must fit inside the other with plenty of spare space.
✅ 150ml carton of cream
✅ Vanilla extract
✅ 3 tsp of caster sugar
✅ Plenty of ice
✅ 6 tblsp of salt
✅ Wooly gloves
1. Put the cream, sugar and vanilla into your first bag (or the small plastic tub). Seal it well. Make sure there are no leaks.
2. Place the ice in the second bag (or large plastic box) and then place the first bag or box inside too.
3. Quickly check that your bag (or box) will close properly before going further. If not, take out a little ice.
4. Now add the salt to the bag /box of ice. Seal it up well.
5. Now put on your gloves and get shaking. Shake shake shake! You will need to shake for about 15 minutes. I can heartily recommend putting on some music for this bit.
6. The ice cream should be frozen, and the outer bag should be full of mostly melted salty ice.
7. Carefully remove the inner bag and enjoy your ice cream!
The Science at Work
Adding salt to pure water changes its MELTING POINT. Salty water melts at a lower temperature than pure water. This means that when we add salt to the ice, it starts melting very quickly.
As the ice melts, it needs to take in energy to do so. This is because, in the solid ice, the particles are vibrating on the spot. In a liquid, like water, they move around slowly. They need some energy to get moving and become a liquid.
In this experiment, the salty ice takes energy out of the cream in order to melt. This causes the cream to freeze.
Key Points
KS2
- The terms solid, liquid and gas.
- How solids, liquids and gasses behave in simple terms.
- Look at examples of melting, freezing, evaporation and condensation.
KS3
- Focus on what is happening to the particles during changes of state. They should be able to draw simple diagrams to show the particles in solids, liquids and gasses, and describe how these particles move.
KS4
- Focus on how the ammount of energy a particle has affects the way it behaves. I.e. the more energy a particle has, the faster it moves and it will spread further apart from the other particles.
KS4
- Link this to how higher temperatures can be used to speed up chemical reactions. Reactions happen when particles collide. Particles that are moving faster will collide harder and more often.
Suggested Extension
Find out about Roman Ice Cream. They didn't use plastic bags, but other than that the process is the same. They put some strange flavourings in! This site is a great starting point.
digventures.com/2015/06/recipe…
Why do we salt the roads in winter?
Ask this question. See if your child can apply what we just learned about salt, water and melting points to explain why this works.
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