The combustion reactions are a type of chemical reactions that occur when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. In simpler terms, combustion is a reaction between a combustible material and an oxidant.
Combustion reactions, like all chemical reactions, are irreversible. Also, they are exothermic, which means that they release heat. However, sometimes the reaction happens so slowly that the change in temperature is not noticeable.
The chemical formula for combustion reactions is as follows:
Hydrocarbon + Oxygen → Carbon dioxide (CO 2 ) + Water (H 2 0)
There are two types of combustion: complete combustion and incomplete combustion.
Complete combustion, also called clean combustion, is one that occurs when the oxidation of a hydrocarbon only produces carbon dioxide and water, which dissipate into the air. In complete combustion, no traces of the burned elements remain.
For its part, incomplete combustion, also called dirty combustion, is that which occurs when the oxidation of a hydrocarbon produces carbon monoxide and soot (for this reason it is “dirty”), in addition to carbon dioxide and water.
Outstanding examples of combustion reactions
1. A lighted wax candle
When we light a wax candle, we start a combustion process. In the beginning, the combustion occurs only in the candle burner. However, once the flame reaches the wax, combustion occurs in the wax as well.
It is a complete combustion because, if allowed to burn, the wax burns until there is no residue left and the carbon dioxide and water are integrated into the air.
2. Burning wood
The hydrocarbons in wood combine with oxygen to form water and carbon dioxide. This is a very energetic reaction, so it generates large amounts of heat and light to release that energy.
It is an incomplete combustion because it generates soot.
3. A lit match
When a match is rubbed against a slightly rough surface, friction generates such heat in the head of the match (composed of phosphorus and sulfur) that it produces a flame. It is an incomplete combustion reaction because there are residues of the waxed paper of the match.
4. Burning coal
Coal burning is a combustion reaction in which coal changes from a solid to a gas. In this reaction, energy is released in the form of heat.
It is an incomplete reaction because, as with wood, it generates soot.
When a firework is lit, the heat causes the chemicals in it to react with oxygen in the atmosphere to produce heat and light. It is an incomplete reaction.
Campfires are examples of combustion that occurs between dry leaves, paper, firewood or any other hydrocarbon and a load of caloric energy (such as a lit match or a spark generated by rubbing between stones).
7. Gas stove
Gas ranges run on propane and butane. These two gases, when they come into contact with an initial charge of heat energy (a match, for example) burn. It is a complete reaction, because it does not generate waste.
8. Strong bases and organic matter
Strong bases such as caustic soda initiate combustion reactions when they come into contact with organic matter .
Wisps are spontaneous flames that are generated in bogs and swamps with a high content of decomposing organic matter.
Said organic matter generates large amounts of hydrocarbon gas, capable of initiating combustion reactions if they come into contact with loads of heat energy.
10. Fuels in engines
Car engines use hydrocarbons to function, with benzine being one of the main ones.
This fuel contains impurities that generate products such as sulfur oxide and nitrogen oxide. Therefore, it is an imperfect combustion.
11. Combustion of methanol
The combustion of methanol, also known as methyl alcohol, is an example of perfect combustion because it does not generate more than water and carbon dioxide.
12. Combustion of magnesium metal
The combustion of magnesium metal is an example of combustion in which neither water nor carbon dioxide is released. In this case, the product is magnesium oxide. It is an incomplete combustion as it produces magnesium oxide.
13. Forest fires
Wildfires are examples of uncontrolled combustion reactions. As with burning wood, they are incomplete combustion reactions because they leave behind residue.
Explosives, such as nitroglycerin and gunpowder, generate combustion reactions that occur in milliseconds. There are weak and strong explosives.
Gunpowder is a weak explosive. In the case of weak explosives, they must be placed in confined spaces (such as the chamber of a gun) in order for them to function.
Nitroglycerin is a strong explosive. Unlike weak explosives, this type of explosive does not require being in a confined space and has a long range, so it destroys everything in its range of action.
17. A lighter
Lighters often contain butane, which when it comes into contact with an ignition spark generates a combustion reaction.
In most cases, it is a perfect combustion because it does not generate unwanted waste, but only carbon dioxide and water.
18. Burnt paper
The organic matter in paper burns on contact with a heat load. It is an example of incomplete combustion because it leaves residue.
19. An oil lamp
Oil lamps are based on water, oil, and a kettle that floats in the oil. The kettle goes into combustion and, as it burns, the oil is consumed.
20. A lit cigarette
Cigarettes ignite when they come into contact with a caloric load. It is an incomplete combustion because it leaves ashes.
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