Today we investigated the effects of adding salt to ice.
We added 2 tsp of salt to a plastic cup of ice and measured the temperature. Most group's ice temperature fell to well below minus 10 degrees Celsius.
We added 2 tsp more of salt and measured the temperature. It fell to between minus 15 degrees and minus 18 degrees. The plastic cups started to frost over!
Why did this happen?
Clue #1: We knew that salt helped ice to melt.
Clue #2: We also remembered that for ice to melt, the water/ice molecules need to be excited and start moving about more. That means the molecules need to draw in energy from somewhere, in order to excite and start moving...
After LOTS of discussion we worked out that the energy to excite the ice was coming from the air around the ice. If ADDING energy warms things up, then removing energy must make things COLDER! So the air around the ice was becoming colder, not the ice. The thermometer was measuring the temperature of the air, not the ice.
And boy, was the air around the ice COLD! Minus 18 degrees Celsius was the coldest reading we made. Did I mention that the plastic cups were frosting up?
What does this mean for Antarctica?
The salty ice all around Antarctica is melting, and energy is needed to keep the process going. That energy comes from the air, and as the energy transfers from the air to the ice, the air temperature drops! Brrrrrrrrrrrrrrr..... No wonder it's so cold down there!
2 comments:
I did not know this. Thank you for posting this and teaching me something room 7.
keep it coming room 7. I am learning lots about your Antarctica study.
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