- Two empty food cans
- Crushed ice (enough to half fill both cans)
- A heaped tablespoon of salt
- Two pieces of damp paper towels, folded into quarters
- A tray to put the two cans on
- Half fill both cans with crushed ice
- Label one can ‘S’ and the other ‘I’
- Place each can on a folded damp paper towel
- Add a heaped tablespoon of salt into the can labeled ‘S’
- Note down your observations after 5 and then 15 minutes
You should notice ice form on one of the cans.
So, what difference does the salt make?
When we mix salt with water it gives us a new material which has a lower freezing point than normal water. This makes everything just that little bit colder in the can labeled ‘S’ in comparison to the can labeled ‘I’.
The ice on the outside of the can is formed as the water in the air around the can is cooled.
Other things you can try:
- Observe and compare how the two paper towels react.
- Use a good thermometer to measure the temperature of the two cans
- Experiment with different containers – glasses, plastic etc – what result do you get and why?
Hope you enjoyed this blog. For those of you that are not enjoying the cold just remember that Thursday was officially the first day of spring in NZ!
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