Although explosions are a form of combustion, but have a lot of differences.
Combustion begins when a substance is warmed a certain temperature, this is also know as temperature of ignition. Combustion produces a heat level above the temperature of ignition, so that the reaction can continue. Once the temperature level gets to a certain point, the substance will begin to gasify and form what we see as fire.
An explosion is different from the combustion of fire in many ways. Explosions are "substances that contain a large amount of energy stored in chemical bonds" (Wikipedia). This is one key difference between combustion and explosions. Explosions rely on the initial combustion or agitation of a substance to give off such massive amounts of energy in such a short period. This is because explosions reactions use substances that combust very quickly, but also in such a manner that it will affect the substance next to it, thus creating a quick but violent chain reaction.
A chain reaction is a "sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events" (Wikipedia).
A chain reaction occurs when a substance with a weak chemical bond is agitated caused the bond to be broken. This broken bond releases large amounts of energy causing the substances next to it to break their bonds. This process will continue until all the substance is used up.
Another key feature of explosions is their ability to produce a shock wave.
When an explosion occurs, it produces a massive blast of energy in the form of waves. These waves are highly destructive and they usually do as much damage as the initial explosion.
- To see a shock wave Click Here
- for just the shock wave watch 0:55 - 1:09
A shock wave is defined as a "sharp change of pressure in a narrow region traveling through a medium, esp. air, caused by explosion or by a body moving faster than sound."
Combustion reactions of fire however don't have that ability, because they aren't combusting fast enough for there to be a sharp change in pressure.
Types of Explosion
There are many different types of explosions, ranging from natural explosions to Mechanical explosion. However since there is such a broad range of explosions, i will only be focusing on two of the most common types.
Those would be Chemical and Nuclear explosions.
You can follow me on my other pages for an explanation on these types of explosions, or by clicking on these links Chemical Explosions or Nuclear Explosions
For more information on the basics of explosions Click Here