This is a good demonstration to show to kids at home or at a school.
What you need:
- Plastic syringe (I used a 12mL monoject. One can buy them cheap in large or small quantities on amazon or ebay.)
- Hot tap water, at around 125F
- Cup for the water
- Optional: Thermometer
Step 1: Pour Water Into Cup
Run hot water from the tap, waiting for it to reach full temperature. Then fill up a cup with the hot water.
Stick a thermometer into it if you like. But don't take too long, or the water will cool off too much.
Step 2: Put Water in Syringe
Gently fill the syringe a little less than 20% full (I put 2mL of water in a 12mL syringe). If you want, you can put a little more in, and then eject bubbles by holding the syringe pointing up and pushing the piston up.
Step 3: Boil the Water!
Press one finger very tightly over the tip of the syringe. Hold the syringe horizontally, and pull back the plunger to the full length of the syringe, gently so it doesn't pop out (it'll take some force). If all goes well, the water should boil for a few seconds along the length of the syringe. You may also notice the syringe steaming up.
Then gently release the syringe. You should notice that everything returns to more or less how it was before the experiment (maybe with a little bit more air, if some leaked in).
It should also boil if you hold the syringe vertically. But then you or your audience might worry that the bubbling is not boiling, but it's just air leaking in and around the piston.
If it doesn't boil, try using less water. Or hotter water. Or alcohol (e.g., heated by putting a small cup of alcohol in a larger cup of hot water).