Relationship between activation energy and melting?

  • #1
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Main Question or Discussion Point

Hello. I know this is a dumb question but I am just learning chemistry.

Ok, for collision theory, atoms need a certain amount of energy to bond, because they need to break old bonds and form new ones. Makes sense

But, at high temperatures, things become gaseous. At low temperatures, things become solid.

Things become solid, aka more bonded together, at low temperature.

So...for activation energy, more energy is needed to create bonds. But, more energy also makes bonds break and become gases. So how is it that more energy = more bonds, but more energy also = less bonds? I was told that you can have more than enough activation energy and the bond will still occur. Does too much energy make it not possible to bond?

Clearly I know I am missing something here.
 

Answers and Replies

  • #2
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Too much energy means you don't get solids, yes.

At surfaces between different phases of a substance, you constantly have some bonds breaking and others forming. With more energy, in general both rates increase, but the rates for solid->liquid->gas increase much faster than the rates in the opposite direction, so if you heat things up they tend to melt and boil.
 
  • #3
Borek
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for activation energy, more energy is needed to create bonds
Something doesn't sound right here. Activation energy is involved in the process of the bond creation, but mostly doesn't affect the bond itself.
 
  • #4
Ygggdrasil
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Ok, for collision theory, atoms need a certain amount of energy to bond, because they need to break old bonds and form new ones. Makes sense
The key point here is that the activation energy is used to break old bonds in order for new bonds to form.

Think of it this way. In a solid, molecules stay bonded to the same neighbors because there is not enough thermal energy for these bonds to be broken. When there is more thermal energy available, the substance becomes a liquid where molecules are constantly breaking and re-forming bonds with their neighbors. Finally, when you have enough thermal energy to completely break any intermolecular bonds, you now have a gas.
 

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