Saturday, September 21, 2013

Why Doesn't The Ocean Freeze Solid?

Ever wonder why the oceans don't freeze solid? Well we have and we decided to investigate to find out. We had to make some cccold water! If you try putting it in the freezer you'll find you end up with ice pretty quickly instead of super cold water. But we found an experiment that showed us how to cool water down to it's freezing point without freezing it solid!

Supplies Needed

Freezer
Spoon
Water
Salt
Ice
two plastic cups (we ended up using two glass canning jars)
marker

Deep Freeze Experiment

1. First fill both plastic cups with the same amount of water.
2. Add four heaping tablespoons of salt to one of the cups. Mark this cup with an S.
3. Place both cups in the freezer and make sure they won't fall over.
4. Check the cups every hour for the first four hours then leave them overnight and check the next morning. What's the difference between the two cups?

What's Going On?

Water normally freezes at around 0 degrees C, but adding salt to the water lowers it's freezing point. The salt makes it more difficult for the water to freeze solid so the water can be be colder that 0 degrees and still not freeze completely. Salty water will eventually freeze, but the water has to be a lot colder than ordinary water.

To prove this check the cup with the plain water. It should freeze in about four hours, but the other cup may not freeze at all. Instead there may be a tiny bit of ice that forms, but only after it gets rid of the salt. To do this the salt sinks to the bottom. The same thing happens in the ocean around Antarctica.

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