Fireproof banknote is a demonstration of putting a

banknote A banknote—also called a bill (North American English), paper money, or simply a note—is a type of negotiable instrument, negotiable promissory note, made by a bank or other licensed authority, payable to the bearer on demand. Banknotes w ...

, previously soaked in 50% ( v/v)

alcohol fuel Various alcohols are used as fuel for internal combustion engines. The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized chemically or biologically, and they have ch ...

solution, to a

flame A flame (from Latin ''flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they ...

. The fire is lit and later extinguished by itself without the banknote being burnt. This demonstration can be used to teach about the

fire triangle The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires. The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fir ...

and classes of fire.

Explanation

A 50% (v/v) alcohol solution is composed of 50% alcohol and 50% water in which water acts as a

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

. By igniting a paper banknote completely soaked with 50% alcohol solution, the alcohol (which is the

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

in the

) is combusted into

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

and

water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

. On the other hand, water is heated up with some being

evaporated Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

as it absorbs energy from the

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...

of alcohol. The evaporation of water helps cool down the system, so not all water is evaporated and the paper banknote is not burnt. The water to alcohol ratio should be 50% or higher; a lower ratio leads to the banknote being slightly burnt because there is not enough water to absorb the combustion energy and cool down the system. C_''n''H_2''n''+1OH + (3''n''/2) O₂ → ''n'' CO₂ + (''n''+1) H₂O Common alcohol fuels for this experiment can be

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

(''n''=1),

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

(''n''=2) and both isomers of

propanol There are two isomers of propanol. * 1-Propanol, ''n''-propanol, or propan-1-ol : CH3CH2CH2OH, the most common meaning *2-Propanol, Isopropyl alcohol, isopropanol, or propan-2-ol : (CH3)2CHOH See also * Propanal (propionaldehyde) differs in sp ...

(''n''=3). The fire lit in this scenario is categorized as a

class B fire In fire classes, a Class B fire is a fire in flammable liquids or flammable gases, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, or alcohols. For example, propane, natural gas, gasoline and kerosene fires are types of Cl ...

(fire from flammable liquids), while the fire from burning paper (banknote) is categorized as class A. The alcohol-water mixture flame can be hard to detect, so

sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

can be added to give the flames an orange-yellow color. For safety purpose, a water tray should be prepared for emergency use in case a paper banknote caught a fire, and flammable and combustible materials should not be kept or put near the flame.

Alternative materials or setups

Other materials

Euro banknotes Banknotes of the euro, the common currency of the Eurozone (euro area members), have been in circulation since the first series (also called ''ES1'') was issued in 2002. They are issued by the national central banks of the Eurosystem or the Eur ...

are recommended since it is made of paper and it is legally permitted to artistically mutilate it or burn in small amounts. Moreover, there are no depictions of any persons on the banknotes. Aside from banknotes, a similar experiment can be performed by using

towel A towel is a piece of absorbent cloth or paper used for drying or wiping a surface. Towels draw moisture through direct contact. In households, several types of towels are used, such as hand towels, bath towels, and kitchen towels. Paper towels ...

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed ...

or exam paper.

Other setups

No material

A solution of about 50% fuel alcohol and 50% water can catch on fire and extinguish itself in a "burning water" demonstration. In contrast to the subsection above, this can be done in a glassware without any absorbing materials like banknotes, towels, or paper.

No fuel

Tap water may be added to a

paper bag A paper bag is a bag made of paper, usually kraft paper. Paper bags can be made either with virgin or recycled fibres to meet customers’ demands. Paper bags are commonly used as shopping carrier bags and for packaging of some consumer go ...

which then is put on a stove to boil. The paper bag can absorb water, which cools down the system and prevents the paper bag from being burnt.

Gallery

File:Fireproof banknote.webm, A video of fireproof banknote experiment File:Fireproof banknote 2.webm, A video of fireproof banknote experiment File:Fireproof banknote 3.webm, A video of fireproof banknote experiment

References

{{commonscat, Fireproof banknote experiment Banknotes Chemistry classroom experiments Articles containing video clips Fire protection