Scientific Concept behind Burning Money
A combustion reaction occurs between alcohol and oxygen, producing heat and light (energy) and carbon dioxide and water.
C2H5OH + 4 O2 -> 2 CO2 + 3 H2O + energy
When the bill is soaked an alcohol-water solution, the alcohol has a high vapor pressure and is mainly on the outside of the material (a bill is more like fabric than paper, which is nice, if you've ever accidentally washed one). When the bill is lit, the alcohol is what actually burns. The temperature at which the alcohol burns is not high enough to evaporate the water, which has a high specific heat, so the bill remains wet and isn't able to catch fire on its own. After the alcohol has burned, the flame goes out, leaving a slightly damp dollar bill.
Here's what you need to do the demonstration...