A combustion reaction or also known as burning is an exothermic chemical reaction where a “fuel” compound is reacted with an oxidant to produce new product of oxide compound and energy which is usually in form of heat and light. During combustion the energy is used, one or more oxides are formed and large of amount of energy is released which can be used to power machine such as cars or burning of coal to run turbines producing electricity. There are two types of combustion, incomplete and complete. Complete combustion occurs when there is plenty of oxygen available and the products are usually carbon dioxide and water. Incomplete combustion occurs when there is less oxygen available; the products usually include carbon (soot) and/or carbon monoxide. Examples of combustion include burning of wood, metals or non-metals in air and hydrocarbons.
Complete Combustion examples:
4Na + 3O2 2Na2O3
CH4 + 2O2 CO2 + 2H2O
S + O2 SO2
Incomplete combustion examples:
2C + O2 2CO
C2H5OH + 2O2 2CO + 3H2O
According to “Kinetic theory of matter”, all matter is composed of particles (molecules, atoms, or ions) which are constantly moving. In solids, the particles can only vibrate in one place. In liquids, they are close together, but move around. In gases, they are far apart and flying in all directions. Kinetic energy is the energy an object possesses due to its motion. Temperature is a measure of the average “KINETIC ENERGY” (rate of motion) of the particles.
As the objects are heated up, their temperature increases so does the kinetic energy due to the added heat energy causes the increase in kinetic energy, therefore at higher temperature the particles move faster.
Example: When the air inside of air balloon is heated up to 1000C by gas burner, the heat energy is added to make the air inside hot. Because gas molecules are not strongly attracted to each other, they are free to move about. Since the hot air is less dense than cool air as a result by the added heat energy force gas molecules apart and cause them to move faster and make collisions harder resulting in massive expansion of air balloon and it starts to float. If the hot air is let out and cool air enters, the air balloon goes down.
Explosions are just the uncontrolled fast reactions with a rapid increase in volume and release of energy in extreme manner, usually with generation of high temperature and release of gases.
Explosions can occur when there are necessary conditions: 1. Fuel molecules are well mixed with air. 2. Source of ignition (spark, or flame). 3. There is no limit of flow of fuel to combustion area.
For example, when a gas leak fills a room the fuel gas is mixed with air, any spark or flame can start reaction that accelerates so fast due to high concentration of gas molecules and oxygen molecules collide vigorously in suitable orientation and with sufficient energy that can break bonds of gas and oxygen to form new bonds, large amount of heat energy released and gas pressure creates a shockwave causing an explosion.
Dust explosion is also one of the major explosions. Many materials which are commonly known to oxidise can generate a dust explosion such as coal, magnesium, grain, flour, powdered metals (aluminium and titanium). There are four necessary conditions for a dust explosion: 1. A combustible dust 2. High concentration of dust is suspended in the air 3. There is an oxidant ( typically atmospheric oxygen) 4. Source of ignition
For example: coal dust can arise from mining of coals. Large piece of coal is difficult to burn in air. However, accumulation of coal dust suspended in air in an enclosed location can cause an explosion if it comes in contact with source of ignition. Since the dust particles have very large surface area due to