Sunday, March 02, 2008

The Sweat Episode - Episode 34

Yes, he's done freezing by boiling before, but this time Dr. Carlson uses liquid nitrogen, a special tube, and a little water to demonstrate the power of sweat!

Science Theater Episode 34: The Sweat Episode

4 comments:

adrissyan said...

Dear Dr. Carlson,

All your videos are excelent.As a Physics teacher I enjoyed them thoroughly and recomended to my students

Rich said...

Dr. Carlson,

I didn't quite follow the setup of the experiment.

Is the left (your right) side of the glass apparatus open? Or is this a closed system?

If it is closed, are you dropping the pressure on the left side by cooling it?

If it is open... are you cooling the air at the transition? Which draws more water into the air?

Dr. Matt J. Carlson said...

The experiment is entirely enclosed in glass. On one side, liquid nitrogen is used to cool the gas inside to reduce the pressure. This causes the water on the other side of the experiment to boil due to low pressure.

The boiling removes heat from the liquid water, causing it to freeze.

(Thus ice is eventually formed on BOTH sides of the apparatus, on one side due to the liquid nitrogen, on the other - due to the heat of vaporization...)

Rich said...

Ah! Thank you -- that makes more sense now.

Nova had a great episode on refrigeration/absolute zero where they showed a similar experiment performed by Faraday.

Nova Transcript

Rich