Uses of Explosions

	 Uses of Explosions
Explosions have been used in warfare and other areas since the 10th century. Originally, explosives relied on a reaction from black powder in order to work. This black powder was a mixture of powdered carbon, sulphur and potassium nitrate and was ignited by a fuse. This process involves oxidation reactions causing product gases of CO2 , SO2 , and N2 . An oxidation when an element?s oxidation state has increased. In the case of the black powder explosion, the increased oxidation state is caused by carbon and sulphur gaining oxygen which they lose electrons to, causing there charge to become more positive. The explosion happens when the gas built up is confined into a small space causing a huge build up in pressure resulting in the explosion. The oxidation within black powder happens very quickly because it carries its own supply of oxygen in the form of potassium nitrate. Mixtures with a higher supply of oxygen to the reactants react more quickly due to an increased rate of oxidation. This technique was used for centuries, but when armies started to use hundreds of weapons, a great deal of white smoke was produced making it impossible for soldiers to see.
An explosive was needed that gave off very little or no smoke. Gun cotton or cellulose nitrate, was accidentally discovered by Dr Christian Schönbein when he spilt a mixture of concentrated sulphuric and nitric acid. He used his wife?s apron to mop it up which later burst into flames in front of a fire whilst drying out. Militaries used this idea and produced mixtures for powders based on cellulose nitrate. These new powders could be far more useful in warfare as they produced very little smoke. Because of this, a lot more of the explosive could be used meaning objects could be propelled at greater speeds with greater forces. The cellulose nitrate used in explosives is in the form of cellulose trinitrate which has a formula of C6H7O11N3. As the formula shows there is a high number of oxygen atoms and is effectively carrying its own source of oxygen allowing the reaction to take place very quickly. This increased force from the reaction started off the uses of bullets and explosive shells replacing muskets and cannon balls. [image]The Structure of Cellulose nitrate Later, in the 1880?s, the British army invented cordite which was a combination of the currently used, cellulose trinitrate, and glycerol trinitrate. During production, propanone is added in order to turn the mixture into a jelly like substance which can be squeezed through small holes emerging as thin cords. The propanone is then dried out leaving a brown powder explosive which is still widely used today. The British army got this supply of propanone from maize imported from America, but during the first world war, they were unable to receive the maize. They had to find another source for extracting propanone which came in the form of conkers. This new source meant they could continue making the cordite required for the shells and bullets. Cordite is used to make, what are know as low explosives for example in guns. One discovery brought about the start of high explosions, larger explosions used to cause damage themselves rather than act as a propellant. The discovery which brought these about was of nitroglycerine. It was discovered by Ascanio Sobrero by mixing concentrated nitric and sulphuric acid and glycerine, leaving behind a yellow oil which was the nitroglycerine. The substance was very unstable and unpredictable, it could be denoted by a very light touch. The conditions under which nitroglycerine would explode unpredictable with times it would explode with very little contact and others it would be difficult to detonate. Alfred Nobel was the man who decided to experiment with the explosive qualities of nitroglycerine and attempt to use it to produce a safe explosive for use in mining. He achieved this by adding kieselguhr to the mixture, this turned it to a paste which could be shaped into rods. These rods would only explode when they were intentionally detonated. These were know as sticks of dynamite. In order to stop the dynamite detonating unintentionally was to use a small amount of gunpowder to trigger the reaction. [image] Image taken from- http://nobelprize.org/nobel/alfred-nobel/biographical/life-work/nitrodyn.html Dynamite was the first high explosive to be produced and was later enhanced by replacing the kieselguhr, with substances which themselves would explode causing greater effect. The development of high explosives continued with the invention of tnt. The difference between tnt an dynamite is that tnt contains nitro groups rather than nitrate groups. This means that tnt does react with metals and can be contained in metal making it useful for bombs. [image]The structure of tnt The explosions of tnt and dynamite work because the reactions take place very quickly and are highly exothermic meaning they give off high amounts of heat with a lot of gas being produced. The high amounts of gas being produced cause an increase in pressure in the confined space. High explosives like dynamite can reach pressures of up to 275000 atmospheres, however low explosives such as the black powder, can only produce around 6000. This is the difference between and explosion being a high explosion or a low explosion. An example of a high pressure increase is in the equation for the nitroglycerine reaction: c3h5n3o9 à 3CO2(g)2½H2O(g)1½N2(g)+¼O2(g) 1 mol of liquid à 7.25 mols of gas The equation shows an increase in the number of mols, this results in an increase in the area taken up, but because of the confined space, the gas has nowhere to go so pressure is produced on the container until it explodes. Although nitroglycerine is most commonly used for dynamite, it was originally experimented with for medical purposes. One use that was discovered was that it relieves the pain from angina pectoris by increasing the amount of blood to the brain and heart. When producing nitroglycerine, workers suffered from headaches. In modern day production, a lot more care and regard to safety is used to prevent the dangers of this and other chemicals.

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