This is a fun demonstration that may be conducted to get students thinking about combustion or just as a spectacular end-of term filler lesson.
Equipment required (per demonstration):
The ethanol and water is mixed 50:50 with about 20ml of each being enough to soak the note. A small pinch of salt (sodium chloride) is added to the mixture so that it burns with a slightly yellow flame. This just makes the flame more visible and is optional, especially if you are in a darkened room.
- paper money (£5 or £10 note)
- ethanol (highly flammable)
- sodium chloride
- Bunsen burner
- heatproof mat
A yellow Bunsen flame is used for this demonstration as a blue flame may burn the note.
The note is usually soaked in the mixture and held briefly in the flame until it ignites. The ethanol in the mixture should burn off completely leaving the damp note intact. As the ethanol burns, some of the water on the note evaporates, cooling it just enough to make sure it does not ignite.