Here is a compilation of demonstrations I do for “Combustion Day”, which capitulates three days of demonstrations to identify the five main types of chemical reactions. DO NOT TRY THESE AT HOME.
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The demo cam is simply an old Sony Handicam Digital 8 camcorder mounted on an inexpensive Videosecu Universal Camera Mounting Bracket.
The camera has an adapter that splits into an RCA video/mono audio cable, which I can easily plug into my classroom television. Switching the input on the TV is a piece of cake, and using the TV doesn’t interfere with the interactive whiteboard.
Here are some of the benefits:
1. I can project demos onto the television above, so the entire class can see every bit of the demonstration.
2. The zoom function is quite impressive; I can easily zoom in on discreet parts of the demonstration not easily seen – even by the person doing the demo. This is made even easier with the use of the remote control.
4. Because I have to use the record function to keep the image on screen, I can easily capture video of the demonstration. As there is a firewire output, I can easily capture the video with a connected laptop, and share it online (below see video demonstration of adding sodium to water).
5. I can also capture slow reactions over a long period of time, import them to a computer and speed up the video to a shorter time (see video of copper in silver nitrate solution).
Some of the Drawbacks:
1. The angle is a little ackward because of the mounting limitations. It takes a little practice not to walk in front of it, and to make sure that the demo is in the viewing area while zooming.
2. In order to use the TV as a monitor, I have to use the record function. This requires me to stand on a stool, and manually rewind the tape every hour (it cannot be done with my remote).
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.
- 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)
Note the rapid condensation that appears on the lab table once the pressure is equalized.
NOTE: this demonstration was done behind a Plexiglas screen when there were no kids in the room. Below is a picture of the bottle before, after, and a piece that was lodged in the ceiling (of which I am quite proud).
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 (see About page). This is why a safe alternative to a live demo is to take an extreme video for future use.
After a few days of unbearable heat in my classroom (no air conditioning in my school), I decided to quantify my misery.
You’ll notice two things:
- My room got hot – up to 85ºF, which was actually cooler than the day before (~89 ºF). Our district touts equity, but seeing as the other high schools in our district both have air conditioning, I can assure you that the district is NOT equitable in providing a classroom environment conducive to learning.
- The other interesting thing is that there is a noticeable change in room temperature when the kids are physically present. Notice the two dips in temperature (marked by the arrows). They represent two hours the chemistry room is vacant. Thus, body heat can significantly raise the temperature of any classroom.
Keeping these two things in mind, I have a suggestion to maintain ‘equity’ – keep rooms cooler in non-air conditioned buildings with lower class sizes!