What makes compounds explosive?

[tumor]

What makes compounds explosive?Oxygen-hydrogen for example?Electrons move to the more stable orbit and loosing energy, but I'm not so sure.Plese help me.

 

[Gokul43201]

Typically, an "explosive" involves solid or liquid compunds reacting to form one or more gaseous products. The large increase in volume (or rather, if contained, the large pressure build-up) is what makes the explosive explode.

The reaction of oxygen with hydrogen has a large enthalpy of reaction ~ 300kJ/mol. This is a lot of heat, if the reaction is allowed to happen uncontrolled. If your question is why there is an positive enthalpy change, then that is due to the electrostatic attraction between the atoms (not just the elctrons). Look up the Lennard-Jones potential and you'll see why it helps (reduces the total energy) to have more atoms sitting in wells. And reducing the energy of the system involves throwing out all the excess energy - that's where the heat comes from.

 

[russ_watters]

Also, things burn at different rates. Some things burn so fast that the burning happens in a shock wave travleing through the substance at the speed of sound. Speed of burning is what determines if something is a high/medium/low explosive or just burns. Chemically though, its as simple as Goku explains: burn something solid and you get heat and a very high volume of gases.

 

[Nenad]

Gokul, if the enthalpy is positive, that means the reaction is endothermic, meaning it is nonspontaneous, and you need energy to make it happen. I think you mean the revese reaction produces a lot of heat. To answer your question is another way, you said it right, the electrons do try to acheve a more stable orbit. Have you ever seen a reaction between an alkili metal and water. Its explosive. This is because the alkili metal has one loosely bound electron, and the polar water molecule wants this electron badly, making the reaction quick and explosive.