Fireproof banknote is a demonstration of putting a banknote, previously soaked in 50% (v/v) alcohol fuel solution, to a flame. The fire is lit and later extinguished by itself without the banknote being burnt. [1] This demonstration can be used to teach about the fire triangle and classes of fire. [1]
A 50% (v/v) alcohol solution is composed of 50% alcohol and 50% water in which water acts as a solvent. [2] By igniting a paper banknote completely soaked with 50% alcohol solution, the alcohol (which is the fuel in the fire triangle) is combusted into carbon dioxide and water vapour. Contrarily water is heated up, with some being evaporated as it absorbs energy from the combustion of alcohol. [2] The evaporating 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. [2]
CnH2n+1OH(aq) + (3n/2) O2(g) → n CO2(g) + (n+1) H2O(g) [1] [2]
Common alcohol fuels for this experiment can be methanol (n=1), [2] ethanol (n=2) [1] and both isomers of propanol (n=3). [2] The fire lit in this scenario is categorized as a class B fire (fire from flammable liquids), while the fire from burning paper (banknote) is categorized as class A. [1] The alcohol-water mixture flame can be hard to detect, so sodium chloride can be added to give the flames an orange-yellow color. [1] [3] 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. [1]
Euro banknotes are recommended since it is made of paper and it is legally permitted to artistically mutilate it or burn in small amounts. [4] Moreover, there are no depictions of any persons on the banknotes. [1]
Aside from banknotes, a similar experiment can be performed by using towels, [2] paper [5] or exam paper. [6]
A solution of about 50% fuel alcohol and 50% water can catch on fire and extinguish itself in a "burning water" demonstration. [7] In contrast to the subsection above, this can be done in a glassware without any absorbing materials like banknotes, towels, or paper.
Tap water may be added to a paper bag 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. [8]
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While activation energy must be supplied to initiate combustion, the heat from a flame may provide enough energy to make the reaction self-sustaining. The study of combustion is known as combustion science.
Ethanol is an organic compound with the chemical formula CH3CH2OH. It is an alcohol, with its formula also written as C2H5OH, C2H6O or EtOH, where Et stands for ethyl. Ethanol is a volatile, flammable, colorless liquid with a characteristic wine-like odor and pungent taste. It is a psychoactive recreational drug, and the active ingredient in alcoholic drinks.
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidity affects rate of evaporation of water. When the molecules of the liquid collide, they transfer energy to each other based on how they collide. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.
A flame 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 are then considered plasma.
Varnish is a clear transparent hard protective coating or film. It is not to be confused with wood stain. It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmented as desired. It is sold commercially in various shades.
Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel, ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.
A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, absorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.
The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires.
A beverage-can stove, or pop-can stove, is a do it yourself, ultralight, alcohol-burning portable stove. It is made using parts from two aluminium beverage cans. Basic designs can be relatively simple, but many variations exist.
A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants may also cool the fuel through physical action or endothermic chemical reactions. Fire retardants are available as powder, to be mixed with water, as fire-fighting foams and fire-retardant gels. Fire retardants are also available as coatings or sprays to be applied to an object.
Fireproofing is rendering something resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a noun, verb or adjective; it may be hyphenated ("fire-proof").
Firefighting foam is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, thus achieving suppression of the combustion. Firefighting foam was invented by the Russian engineer and chemist Aleksandr Loran in 1902.
A kerosene heater, also known as a paraffin heater, is typically a portable, unvented, kerosene-fueled, space heating device. In Japan and other countries, they are a primary source of home heat. In the United States and Australia, they are a supplemental heat or a source of emergency heat during a power outage. Most kerosene heaters produce between 3.3 and 6.8 kilowatts.
A fire class is a system of categorizing fire with regard to the type of material and fuel for combustion. Class letters are often assigned to the different types of fire, but these differ between territories; there are separate standards for the United States, Europe, and Australia. The fire class is used to determine the types of extinguishing agents that can be used for that category.
A compressed air foam system is used in firefighting to deliver fire retardant foam for the purpose of extinguishing a fire or protecting unburned areas.
A combustible material is a material that can burn in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.
A flame arrester, deflagration arrester, or flame trap is a device or form of construction that will allow free passage of a gas or gaseous mixture but will interrupt or prevent the passage of flame. It prevents the transmission of flame through a flammable gas/air mixture by quenching the flame on the high surface area provided by an array of small passages through which the flame must pass. The emerging gases are cooled enough to prevent ignition on the protected side.
Isopropyl alcohol is a colorless, flammable organic compound with a pungent alcoholic odor.
A cool flame or invisible flame is a flame having a typical temperature of about 400 °C (752 °F). It is usually produced in a chemical reaction of a certain fuel-air mixture. In contrast to an ordinary flame, the reaction is not vigorous and releases little heat, light, or carbon dioxide. Cold flames are difficult to observe and are uncommon in everyday life, but they are responsible for engine knock – the undesirable, erratic, and noisy combustion of low-octane fuels in internal combustion engines.
A pool fire is a type of diffusion flame where a layer of volatile liquid fuel is evaporating and burning. The fuel layer can be either on a horizontal solid substrate or floating on a higher-density liquid, usually water. Pool fires are an important scenario in fire process safety and combustion science, as large amounts of liquid fuels are stored and transported by different industries.
