Nonburning Money

Age

Elementary School, Middle School, High School

Format

Stage Show, Hands-on

Materials

   50/50 (v/v) solution of isopropyl alcohol and distilled water
   2 100 mL beakers
   A dollar
   Firestarter
   Tongs
   Tweezers 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. To avoid burns the flaming dollar/towel must be handled with care at all times. Combustible materials should NOT be in the vicinity, and a fire extinguisher should be readily available. Isopropyl alcohol can damage the eyes severely, so safety goggles should be worn when preparing for and performing this demonstration. Gloves are also a must. Safety never takes a vacation.

Isopropyl Alcohol MSDS

Preparation

Ensure that there is enough of the nonburning solution for the show you are performing. If possible, dim the lights before performing this demonstration.

Demonstration

1. Pick up the dollar with tweezers and place it in about 40 mL of nonburning solution. Allow the dollar to soak up the isopropyl and water for at least one minute.

2. Pick up the dollar with tongs and hold it over a spot in your presentation area away from the alcohol solution.

3. Light the dollar from the bottom and allow the flame to travel up the bill.

What to Say

What normally happens when you light paper on fire? This is just your normal, run of the mill dollar bill. (You may pass the bill around here. Then begin to soak it in the nonburning solution.) This solution is made up of 50% water and 50% isopropyl alcohol. As it is sitting in the beaker, the dollar is soaking up both the water and alcohol. When a minute has elapsed and the dollar has soaked long enough, pull it out of the solution and move the solution away from the area where you intend to ignite the bill. Ask, what do you think will happen if I try to light this dollar on fire? Let’s find out.

Okay, so the dollar is on fire, but it is not burning. How is this possible? This is possible because the alcohol the dollar was soaked in is a highly flammable substance. It has a low vapor pressure as compared to the water in the solution. So the alcohol lights aflame while the water which has absorbed into the dollar never gets hot enough to fully evaporate. So the dollar does not burn. When the alcohol has all burned away the flame extinguishes.

When you are sure that the dollar is cool enough to handle, you can pass the dollar around to the students again to show them that the actual dollar was not burned at all (hopefully).

Why It Is

Alcohol is a volatile, highly flammable chemical. Therefore, when we tried to light the dollar on fire, the alcohol lit on fire, but the water that was absorbed into the dollar protected it from burning. If the alcohol stayed on fire longer there is the possibility that all of the water would evaporate and then the bill itself would light on fire.

This is a good demonstration for older kids and high school students because you can discuss chemical reactions. The reaction performed here was a combustion reaction because the reactants included an organic molecule (isopropyl alcohol) and oxygen, which yielded carbon dioxide and water. Note the highly negative reaction energy, indicating that this reaction is highly exothermic.

2 C3H7OH (l) + 9 O2 → 6 CO2 (g) + 8 H2O (g) -1987 kJ/mole

For younger students, it may be enough to say that the alcohol in the solution burns easily. This substance will burn off quickly and the dollar will not burn at all.

Real Life Examples

You can tell the audience about other alcohols, such as methanol, and ethanol. Methanol is known as wood alcohol, is present in antifreeze, solvent and fuel. Methanol is poisonous because when in the body it is broken by alcohol dehydrogenase into formic acid and formaldehyde. Formaldehyde is the chemical used to preserve bodies after death. If ingested it leads to damage of the optic nerve. Ethanol or grain alcohol is the common type of alcohol present in wine, beer and other spirits. Ethanol is now being tested as a fuel for vehicles. It has long been used as antiseptic and even as an antidote to methanol poisoning.

Mention that we have another demonstration in which we show the extreme flammability of volatile alcohols. In methanol cannons we put methanol into a water cooler and allow the methanol to vaporize. When the vapor is introduced to fire, the methanol lights on fire and flames erupt out of the bottle.