There are few more effective ways to teach science than by showing someone something that clearly relies on magic, and then explaining how it’s actually no different from the processes we see going on all around us every day.
This kind of demonstration challenges us to reexamine “common sense” and things we thought we were certain about. Something should fall down when it tips over – except, you know, when it refuses to. Also, a liquid has to get hot to boil … but this turns out to be a bit of an oversimplification.
A hand boiler is nothing more than two glass bulbs with some liquid and gas inside, connected with a decoratively twisted tube. When you hold the larger bulb in one hand, it heats up very slightly, raising the pressure at that end and forcing liquid into the other bulb.
Note that the liquid doesn’t actually boil: some gas can also be pushed through the pipe and emerge as bubbles on the other side. The lesson here, namely that “appears to be” is always a good hedge to include in a lab report, is already one worth knowing.
You don’t normally select the color or design; presumably, the manufacturer just picks up whichever is closest to hand and plops it into a box. All are equally attractive, though, and they will send a particular color if you specifically request it.
They are made of glass instead of plastic, as the latter would probably not be rigid enough, but this does make them very fragile. A deliveryman having a bad day might mean you could receive this in pieces, while it’s certainly not a toy suitable for small children.
Finally, it’s worth noting that this hand boiler is designed to work best at “room temperature” (ambient pressure probably doesn’t matter too much). Now, science’s “standard” temperature can be defined as either 0°C, 20°C, or 25°C (about 32°F, 68°F, or 77°F) depending on what exactly you’re measuring. There’s no way of knowing what optimum temperature the manufacturer decided on for this demonstration of vapor-liquid equilibrium. If you’re having trouble getting it to work correctly, therefore, all you may need to do is turn on the air conditioning or heater.