It’s something the we do every once and a while. There will be some event for middle to high school students that has something to do with science. So, the department (Chemistry and Physics) will set up some type of demo stations for the kids. Usually some of our physics and chemistry majors are in charge of interacting with the younger kids. It’s a great opportunity for our majors.

But there are some demos that work well and some that don’t work so great. Recently we participated in STEM Fest. Basically a whole bunch of “vendors” set up tables for kids to come by and see science stuff (Science Technology Engineering Math). With that, you want a demo that can meet the following conditions:

• Relatively easy to set up (no particle accelerators).
• Visually attractive to normal humans. Something that could be seen from a distance that a person might say “hey, what’s that? Let’s check it out”.
• Has some type of explanation that can at least START a discussion about science. Hopefully something that our chemistry and physics majors could use to engage in a conversation.
• It would be nice if it could engage multiple (maybe like 5-10) kids at one time.

With that in mind, I want to go over the stuff we used (and some things I saw other tables using) and talk about how well they worked. In a future post (or multiple posts) I would like to give a more detailed description of each demo with key ideas for our students to use in when starting a conversation.

Liquid Nitrogen Balloons

Fortunately, we often have left over liquid nitrogen in our department. This demo could be anything—but we normally take a bunch of balloons and stuff them into the cold liquid so that they shrink. When you pull them out, they expand. It’s very visual and quick to perform. You can also put some liquid nitrogen in a styrofoam cup and let student blow air onto it. This cause the cold air in the cup to move and make water vapor (plus they can feel it).

Overall, this is a pretty good demo. It was a big hit at STEM Fest. Really, the only bad thing is that you need liquid nitrogen. If you don’t have that, then you don’t have anything. In terms of setup, we did bring the large dewar of liquid nitrogen, so that’s a little bit of a pain—but the balloons are small and cheap.

Dry Ice Bubbles

I really didn’t pay too much attention to this demo. I think it’s a flask with dry ice connected to a tube with a funnel on the end. When you dip the funnel into soap, the expanding carbon dioxide fills the balloon. Simple.

This looks easy to setup, but it didn’t draw as big of a crowd as the liquid nitrogen. But it’s so easy to do that it seems like a nice one to include.

Concave Mirror

We have this large parabolic mirror. My intention was that kids could use this to project an image onto a piece of paper (I made a small frame to hold tracing paper). But you can also just look at it and see a real image of your hand (it looks like you can grab your own image).

This should always be included with demos. It’s super easy to set up. You just need to put it where people can see and they will often figure out their own demos to do with it. The screen projection didn’t really work—you need some type of very bright source to make a projection.

I would like to make one modification to this setup. If there was some kind of marker (like a ring stand) at the appropriate location for the viewing location, it would be easier to see how to grab your hand image. That seems easy to set up.

Polarized Light and an LCD Monitor

I have an older LCD monitor with a the front polarizer removed (a student did this for me a while ago). There’s a large (external) polarizer. When students hold this up, you can see the image on the monitor. Without the external polarizer, it’s just a white screen. Oh, I’m running an old Apple TV with a screen saver to produce an image.

Again, this is pretty easy to setup (assuming you have electrical power). It’s not super appealing from a large distance, but when kids get up close they seemed to enjoy it.

Chemistry Gak

I didn’t have anything to do with this demo (you know, chemistry). Basically, kids come by and mix together stuff to make gak (a type of fun putty or something). The kids like it, but they have to sit down for a moment to make the stuff. You could probably do about 3-4 students at a time.

You can’t really see this demo from far away. A human would have to decide to go up to the table to figure out what’s going on. Also, it requires a bunch of supplies to be carried into the event. However, in the end the kids get something to take away (the gak). We always do this one.

Vacuum Bag

We didn’t do this one, but I saw another group use it. The idea is to take a human and put them in a large plastic bag (with their head sticking out). Then you use a vacuum cleaner (or pump) to remove the air from the bag. The atmospheric air pressure then locks the person in place and they can’t move.

It’s a great demo, but not really for large crowds. It takes a few minutes for a person to work through the demo and other people can just observe. Also, it sort of scares me. A kid could get freaked out or have trouble breathing. Even worse, they might try this one on their own and do it wrong (and dangerous).

OK, there are more demos—but those are the ones we used recently. Next time we have an event, I will add any new stuff we used.