An explosion is a rapid increase in volume Volume is how much three-dimensional space a substance or shape occupies or contains, often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container, i. e. the amount of fluid (gas or liquid) that the container could hold, rather than the amount of and release of energy In physics, energy is a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state in an extreme manner, usually with the generation of high temperatures Historically, two equivalent concepts of temperature have developed, the thermodynamic description and a microscopic explanation based on statistical physics. Since thermodynamics deals entirely with macroscopic measurements, the thermodynamic definition of temperature, first stated by Lord Kelvin, is stated entirely in empirical, measurable and the release of gases Gas is one of four classical states of matter. Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms. An explosion creates a shock wave A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma) or in some cases in the absence of a material medium, through a field such as the electromagnetic field. Shock waves are characterized by an abrupt, nearly discontinuous change in the. If the shock wave is a supersonic Sounds are travelling vibrations in an elastic medium. In gases sound travels longitudinally at different speeds, mostly depending on the molecular mass and temperature of the gas; (pressure has little effect). Since air temperature and composition varies significantly with altitude, Mach numbers for aircraft can change without airspeed varying detonation Detonation involves an exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. They are observed in both conventional solid and liquid explosives, as well as in reactive gases. The velocity of detonations in solid and liquid explosives is much higher than that in gaseous ones, which, then the source of the blast is called a "high explosive An explosive material, also called an explosive, is a substance that contains a great amount of stored energy that can produce an explosion, a sudden expansion of the material after initiation, usually accompanied by the production of light, heat, and pressure. An explosive charge is a measured quantity of explosive material". Subsonic shock waves are created by low explosives An explosive material, also called an explosive, is a substance that contains a great amount of stored energy that can produce an explosion, a sudden expansion of the material after initiation, usually accompanied by the production of light, heat, and pressure. An explosive charge is a measured quantity of explosive material through the slower burning process known as deflagration Deflagration is a technical term describing subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Most "fire" found in daily life, from flames to explosions, is technically deflagration. Deflagration is different from detonation (which is.

Causes

Natural

Explosions can occur in nature. Most natural explosions arise from volcanic A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface processes of various sorts. Explosive volcanic eruptions occur when magma Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and may also exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and gas bubbles. Magma often collects in magma chambers that may feed a volcano or turn into a pluton. Magma is capable of intrusion rising from below has much dissolved gas in it; the reduction of pressure Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure as the magma rises causes the gas to bubble out of solution, resulting in a rapid increase in volume. Explosions also occur as a result of impact events An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream. Explosions can also occur outside of Earth in the universe in events such as supernova A supernova is a stellar explosion that is more energetic than a nova. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire. Explosions frequently occur during Bushfires A bushfire is a fire that occurs in the bush (collective term for scrub, woodland or grassland of Australia, New Zealand, New Caledonia). In south east Australia, bushfires tend to be most common and most severe during summer and autumn, in drought years, and particularly severe in El Niño years. Southeast Australia is fire prone, and warm and in Eucalyptus Eucalyptus is a diverse genus of flowering trees (and a few shrubs) in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia. There are more than 700 species of Eucalyptus, mostly native to Australia, and a very small number are found in adjacent areas of New Guinea and Indonesia and one as far north as the forests where the volatile oils in the tree tops suddenly combust^[1].

Chemical

The most common artificial explosives An explosive material, also called an explosive, is a substance that contains a great amount of stored energy that can produce an explosion, a sudden expansion of the material after initiation, usually accompanied by the production of light, heat, and pressure. An explosive charge is a measured quantity of explosive material are chemical In chemistry, a chemical substance is a material with a specific chemical composition explosives, usually involving a rapid and violent oxidation Redox describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the reaction that produces large amounts of hot gas. Gunpowder Gunpowder, also called black powder, is a mixture of sulfur, charcoal, and potassium nitrate. Gunpowder can be made just using potassium nitrate and charcoal, but without the sulfur, the powder is not as strong. It burns rapidly, producing a volume of hot gas made up of carbon dioxide, water, and nitrogen, and a solid residue of potassium sulfide was the first explosive to be discovered and put to use. Other notable early developments in chemical explosive technology were Frederick Augustus Abel Sir Frederick Augustus Abel, 1st Baronet FRS was an English chemist. (The Chambers Biographical Dictionary gives his year of birth as 1826.)'s development of nitrocellulose Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton in 1865 Year 1865 was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Friday of the 12-day slower Julian calendar) and Alfred Nobel Alfred Bernhard Nobel ( pronunciation ) (Stockholm, Sweden, 21 October 1833 – Sanremo, Italy, 10 December 1896) was a Swedish chemist, engineer, innovator, armaments manufacturer and the inventor of dynamite. He owned Bofors, a major armaments manufacturer, which he had redirected from its previous role as an iron and steel mill. Nobel held 355's invention of dynamite Dynamite is an explosive material based on the explosive potential of nitroglycerin, initially using diatomaceous earth or another absorbent substance such as sawdust as an absorbent. It was invented by Swedish chemist and engineer Alfred Nobel in Krümmel (Geesthacht, Schleswig-Holstein, Germany), and patented in 1867 in 1866 Year 1866 was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day-slower Julian calendar).

Nuclear

A nuclear weapon is a type of explosive weapon that derives its destructive force from the nuclear reaction of fission or from a combination of fission and fusion. As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives available, with a single weapon capable of completely destroying an entire city.

Electrical

A high current electrical fault can create an electrical explosion by forming a high energy electrical arc An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. The phenomenon was first described by Vasily V. Petrov, a Russian scientist who discovered it in 1802. An archaic term is voltaic arc as used which rapidly vaporizes metal and insulation material. This arc flash An arc flash is a type of electrical explosion that results from a low impedance connection to ground or another voltage phase in an electrical system hazard is a danger to persons working on energized switchgear The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is important. Also, excessive magnetic pressure within an ultra-strong electromagnet An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases can cause a magnetic explosion.

Vapour

Boiling liquid expanding vapour explosions BLEVE , is an acronym for boiling liquid expanding vapor explosion. This is a type of explosion that can occur when a vessel containing a pressurized liquid is ruptured. Such explosions can be extremely hazardous are a type of explosion that can occur when a vessel containing a pressurized liquid is ruptured, causing a rapid increase in volume as the liquid evaporates.

Astronomical

Among the largest known explosions in the universe are supernova A supernova is a stellar explosion that is more energetic than a nova. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire, which result from stars exploding, and gamma ray bursts Gamma-ray bursts are flashes of gamma rays associated with extremely energetic explosions in distant galaxies. They are the most luminous electromagnetic events occurring in the universe. Bursts can last from milliseconds to nearly an hour, although a typical burst lasts a few seconds. The initial burst is usually followed by a longer-lived ", whose nature is still in some dispute. Solar flares A solar flare is a large explosion in the Sun's atmosphere that can release as much as 6 × 1025 joules of energy. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies are an example of explosion common on the Sun The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers , about 109 times that of Earth, and its mass (about 2 × 1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen, while the rest is, and presumably on most other stars A star is a massive, luminous ball of plasma held together by gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. Historically, the most prominent stars on the celestial sphere were grouped together into constellations as well. The energy source for solar flare activity comes from the tangling of magnetic field Magnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field lines resulting from the rotation of the Sun's conductive plasma In physics and chemistry, plasma is a gas in which a certain portion of the particles are ionized. The presence of a non-negligible number of charge carriers makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma, therefore, has properties quite unlike those of solids, liquids, or gases and is. Another type of large astronomical explosion occurs when a very large meteoroid or an asteroid Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids. The term "asteroid" has historically been applied primarily to minor planets of the inner Solar System, as the outer Solar System impacts the surface of another object, such as a planet A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.[a].

Mechanical

Strictly a physical process, as opposed to chemical or nuclear, eg, the bursting of a sealed or partially-sealed container under internal pressure is often referred to as a 'mechanical explosion'. Examples include an overheated boiler or a simple tin can of beans tossed into a fire. A boiling liquid expanding vapor explosion (BLEVE) (see above) is one type of mechanical explosion, but depending on the contents of the container, the effects can be dramatically more serious - consider a propane tank in the midst of a fire. In such a case, to the limited effects of the simple mechanical explosion when the tank fails are added the chemical explosion resulting from the released (initially liquid and then almost instanteaously gaseous) propane in the presence of an ignition source. For this reason, emergency workers often differentiate between the two events.

Properties of explosions

Force

Explosive force is released in a vertical direction to the surface of the explosive. If the surface is cut or shaped, the explosive forces can be focused to produce a greater local effect; this is known as a shaped charge A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, initiate nuclear weapons, in the oil and gas industry and to penetrate armor. A typical modern lined shaped charge can penetrate armor steel to a depth of 7 or more times the diameter of the charge's cone ,.

Velocity

Rapidity of reaction distinguishes the explosive reaction from an ordinary combustion reaction by the great speed with which it takes place. Unless the reaction occurs rapidly, the thermally expanded gases will be dissipated in the medium, and there will be no explosion. Again, consider a wood or coal fire. As the fire burns, there is the evolution of heat and the formation of gases, but neither is liberated rapidly enough to cause an explosion. This can be likened to the difference between the energy discharge of a battery An electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Since the invention of the first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power source for many household and industrial applications. According to a 2005 estimate, the, which is slow, and that of a flash capacitor A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors a static electric field develops in the dielectric that stores energy and produces a mechanical force between the conductors. An ideal capacitor is like that in a camera A camera is a device that records/stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images. The modern camera evolved from the camera obscura flash, which releases its energy all at once.

Evolution of heat

The generation of heat in large quantities accompanies most explosive chemical reaction. The exceptions are called entropic explosives and include organic peroxides such as acetone peroxide^[2] It is the rapid liberation of heat that causes the gaseous products of most explosive reactions to expand and generate high pressures Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. This rapid generation of high pressures of the released gas constitutes the explosion. The liberation of heat with insufficient rapidity will not cause an explosion. For example, although a pound of coal yields five times as much heat as a pound of nitroglycerin Nitroglycerin , (United States spelling) also known as nitroglycerine, (UK spelling), trinitroglycerin, trinitroglycerine, 1,2,3-trinitroxypropane and glyceryl trinitrate, is a heavy, colorless, oily, explosive liquid obtained by nitrating glycerol. Since the 1860s, it has been used as an active ingredient in the manufacture of explosives,, the coal cannot be used as an explosive because the rate at which it yields this heat is quite slow.

When a chemical compound is formed from its constituents, heat may either be absorbed or released. The quantity of heat absorbed or given off during transformation is called the heat of formation The standard enthalpy of formation "standard heat of formation" of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states . Its symbol is ΔHfO or ΔfHO. Heats of formations for solids and gases found in explosive reactions have been determined for a temperature of 15 °C and atmospheric pressure, and are normally given in units of kilocalories per gram-molecule. A negative value indicates that heat is absorbed during the formation of the compound from its elements; such a reaction is called an endothermic reaction. In explosive technology only materials that are exothermic—that have a net liberation of heat—are of interest. Reaction heat is measured under conditions either of constant pressure or constant volume. It is this heat of reaction that may be properly expressed as the "heat of explosion."

Initiation of reaction

A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat. Many substances not ordinarily classed as explosives may do one, or even two, of these things.

For a chemical to be an explosive, it must exhibit all of the following:

(1) Formation of gases

(2) Evolution of heat

(3) Rapidity of reaction

(4) Initiation of reaction

A reaction must be capable of being initiated by the application of shock, heat, or a catalyst (in the case of some explosive chemical reactions) to a small portion of the mass of the explosive material. A material in which the first three factors exist cannot be accepted as an explosive unless the reaction can be made to occur when desired.^{[citation needed]}

Fragmentation

Fragmentation is the accumulation and projection of particles as the result of a high explosives detonation. Fragments could be part of a structure such as a magazine. They could be part of an ordnance case such as a projectile body or a bomb body. High velocity, low angle fragments can travel hundreds or thousands of feet with enough energy to initiate other surrounding high explosive items, injure or kill personnel and damage vehicles or structures.

Notable explosions

Chemical explosions

• Nanaimo mine explosion 1887
• Halifax Explosion 1917
• Battle of Messines 1917
• Oppau explosion, Ludwigshafen, Germany 1921
• Bombay Explosion (1944)
• Port Chicago disaster 1944
• RAF Fauld explosion 1944
• Texas City Disaster 1947
• Nedelin catastrophe 1960
• Soviet N1 rocket explosion 1969
• Flixborough disaster 1974
• PEPCON disaster, Henderson, Nevada 1988
• Ryongchon disaster 2004
• 2005 Hertfordshire Oil Storage Terminal fire 2005
• Albania explosion Gerdec 2008
• Cataño oil refinery fire 2009

Nuclear testing

• Trinity test
• Castle Bravo
• Tsar Bomba

Use in war

• Atomic bombings of Hiroshima and Nagasaki

Exploding volcanoes

• Santorini
• Krakatoa
• Mount St. Helens
• Mount Tambora
• Mount Pinatubo
• Yellowstone Caldera

See also

• Deflagration
• Detonation
• Dust explosion
• Explosive limit
• Fuel tank explosion
• Implosion (mechanical process)
• Underwater explosion
• Mushroom cloud
• Explosion protection
• Piston engine
• Internal combustion engine
• plofkraak

References

1. ^ http://www.theage.com.au/national/fire-power-equalled-1500-atomic-bombs-20090521-bh7r.html?page=-1
2. ^ Dubnikova, Faina; Ronnie Kosloff, Joseph Almog, Yehuda Zeiri, Roland Boese, Harel Itzhaky, Aaron Alt, Ehud Keinan (2005-02-01). "Decomposition of Triacetone Triperoxide Is an Entropic Explosion". Journal of the American Chemical Society 127 (4): 1146–1159. doi:10.1021/ja0464903. http://dx.doi.org/10.1021/ja0464903. Retrieved 2010-02-01.

Categories: Hazards | Explosions

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