Why won't C4 explode when heated but a shockwave can set it off?

[Serj]

I asked my chem teacher but they had no answer so maybe you guys know. Why is it that C4 won't explode when heated (why does it burn slowly?) but a shockwave will set it off?

 

[DrMark]

I asked my chem teacher but they had no answer so maybe you guys know. Why is it that C4 won't explode when heated (why does it burn slowly?) but a shockwave will set it off?

Simply put there are 2 different reaction mechanisms. This is not all that uncommon. In some polymer reactions

nA + Δ -> A_n while if severely stirred nA -> garbage.

The second example is a mechanical process of braking bonds. An common household example of this is egg whites. No matter how much heat you apply to an egg while you will never end up with a meringue. When you beat the egg whites you are actually braking bonds (yes you are also aerating it).

 

[ravenprp]

The reason why C4 does not explode when heated but can be set off by a shockwave has to do with the concept of activation energy. Activation energy is the minimum amount of energy required to start a chemical reaction. In the case of C4, the activation energy for the reaction to cause an explosion is very high, meaning that a significant amount of energy is needed to initiate the reaction.

When C4 is heated, it does not reach the activation energy threshold, so the reaction does not occur quickly enough to cause an explosion. However, when a shockwave is applied, it delivers a sudden burst of energy that exceeds the activation energy, causing the C4 to rapidly react and explode.

This is why C4 is designed to be stable and only detonate when a specific amount of energy is applied, such as through a detonator or a shockwave. It is a safety feature that prevents accidental explosions from occurring due to heat or fire. I hope this explanation helps clarify the concept of activation energy and its role in the behavior of C4.