It is very easy to boil water in a paper cup. It may not be a practical way to boil water, but it's a great way to teach kids (and maybe yourself) a few things, like:

1. You can't always predict the outcome of a situation based upon intuition. Paper should always burn when exposed to fire, and the outside of the cup is dry, so why doesn't it burn?

2. You can boil water in almost anything that will contain it, so the story about aborigines dropping hot rocks in a wooden cup to boil water is true.

3. There are things you can do in the home that will teach you science without destroying your kitchen.

How to do it:

  • Step 1 - take a simple paper cup - it won't work with an insulated or double-walled cup, or a waxed paper cup, or two nested cups. Just a bog standard paper dixie cup.
  • Step 2 - Fill the cup with water (only water.) If you want to make tea, get a bag ready.
  • Step 3 - Put it on the stove. If you have electric burners instead of gas, you need to trim the paper ridge at the bottom of the cup so that the surface of the cup rests against the metal.
  • Step 3 - Heat. Soon the water will boil.
  • Step 4 - Add tea bag if desired.
Why it works:

The water acts as a heatsink, removing the heat of the flame (or hot plate) from the paper, keeping the temperature below the ignition point. Paper burns at more than twice the temperature water boils. As long as there is water in the cup, it will not burn.

This is directly related to a very mean bar trick.

BlueDragon says re Boiling water in a paper cup: Interesting :) Those hot rocks are called pot boilers