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

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In summary, C4 will not explode when heated because the heat does not provide enough energy to break the bonds between the molecules. However, a shockwave will cause a sudden and violent breakage of these bonds, resulting in an explosion. This is due to the different reaction mechanisms involved in heating and shockwaves.
  • #1
Serj
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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?
 
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  • #2
Serj said:
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 -> An 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).
 
  • #3


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.
 

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

What is activation energy?

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is often described as the "energy barrier" that must be overcome for the reaction to take place.

Why is activation energy important?

Activation energy is important because it determines the rate at which a chemical reaction will occur. Higher activation energy means a slower reaction, while lower activation energy means a faster reaction.

How is activation energy related to temperature?

Increasing the temperature of a system will increase the amount of kinetic energy of the particles, making them more likely to overcome the activation energy and react. This is why reactions typically occur faster at higher temperatures.

Can activation energy be negative?

No, activation energy cannot be negative. It is always a positive value, as it represents the minimum amount of energy required for a reaction to occur.

How can activation energy be lowered?

Activation energy can be lowered by using a catalyst, a substance that speeds up a reaction by providing an alternative pathway with a lower activation energy. Catalysts do not alter the overall energy change of the reaction, but they make the reaction occur faster by lowering the energy barrier.

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