Lab Out Loud » classroom

Extreme Phase Change!

Brian — Sun, 05 Oct 2008 01:43:45 +0000

Usually the during the week of homecoming, my Biophysical Science class is just finishing up a basic chemistry unit on the properties of matter. To keep the kids focused on science, I make sure to obtain a little dry ice to have my students observe a unique phase change known as sublimation.

We observe:

Sublimation of dry ice
Density of carbon dioxide (bubbles with hover over more dense carbon dioxide – see video)
Carbon Dioxide as a liquid (under pressure) as it exists in a gas cylinder
Carbon Dioxide as a liquid (by sealing off a pipette with pliers, students can safely observe carbon dioxide liquefy as the pressure increases – see phase change diagram of carbon dioxide)
Rapid sublimation of carbon dioxide in water in a sealed Nalgene bottle (see videos below)

CO2 Expansion 2007 from Brian Bartel on Vimeo.

Note the rapid condensation that appears on the lab table once the pressure is equalized.

CO2 Expansion 2008 from Brian Bartel on Vimeo.

NOTE: this demonstration was done behind a Plexiglas screen when there were no kids in the room. Below are pictures of the bottle before, after, and a piece that was lodged in the ceiling (of which I am quite proud).

Nalgene Bottle Before Phase Change

Nalgene Bottle After Phase Change

Bottle Piece Lodged in Ceiling

I should emphasize that this rapid buildup of gas pressure can be very dangerous. In fact, the rapid vaporization of liquid nitrogen in a sealed plastic container is exactly how I once blew up a sink. This is why a safe alternative to a live demo is to videotape it for future use.

Episode 13 – The Who and What of the Why Files

Brian — Mon, 07 Apr 2008 19:36:27 +0000

This week we talk to Terry Devitt from WhyFiles.org.

Preview from the Show:
Our primary mission is to look at what is going on in the world every week and find some corner of the scientific enterprise that lends itself to a public conversation about science, and then we drill down into that, to contact the best experts that we can find to try to shed light on those dark corners of science – the places and things that people don’t know about, and to provide more than what you’re going to get in a straight-up treatment of science than one routinely encounters in popular media. I think it’s safe to say that after we complete our formal educations, most people only encounter science through popular media, and so a big part of the Why Files mission is to help people come to grips with science – what it is, why it’s important, why it makes a difference in our lives on a daily basis.

It’s really essential that people in a democracy have some understanding of how we generate knowledge, because it impacts our lives in important ways every day.

Links:
Why Files Educator Page
Why Files Classroom Materials
The Why Files Archives
Baseball Spring Training
The Science of Polling
CSI’s: Cool Science Images

Lab Out Loud » classroom

Extreme Phase Change!

Episode 13 – The Who and What of the Why Files

Episode 6 – Adam Rogers from WIRED Science