Enthalpy of Intramolecular Forces

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Mike Vinci 2B
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Enthalpy of Intramolecular Forces

Postby Mike Vinci 2B » Thu Jan 11, 2018 12:18 pm

Hey Chemistry Community, I understand that the bonds between atoms and molecules give off and absorb energy during phase changes, however I was also wondering if such intramolecular forces like van Der wall forces, dipole-dipole forces, or hydrogen bonds give off or receive energy due to phase changes. Comments help. Thanks.

Kailey Brodeur 1J
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Joined: Thu Jul 27, 2017 3:00 am

Re: Enthalpy of Intramolecular Forces

Postby Kailey Brodeur 1J » Thu Jan 11, 2018 1:48 pm

I don't think that the intramolecular forces are affected because these are the forces that hold the actual molecules together. The molecules themselves are not changing when a phase change occurs, just the way the molecules are arranged. By altering the intramolecular forces, a chemical change would occur so I do not think that these forces can give off or take in energy. Only intermolecular forces determine physical properties.

Cyianna 2F
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Joined: Wed Nov 16, 2016 3:04 am

Re: Enthalpy of Intramolecular Forces

Postby Cyianna 2F » Thu Jan 11, 2018 1:52 pm

That's a good question! I'm actually curious about that as well. Although Van Der Waal forces are relatively weak and fluctuate due to the movement of electrons, I think energy is still released/absorbed in any phase change.

Michelle Nguyen 2L
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Joined: Fri Sep 29, 2017 7:03 am

Re: Enthalpy of Intramolecular Forces

Postby Michelle Nguyen 2L » Fri Jan 12, 2018 8:04 am

Phase changes are physical and not chemical changes. They result from forces such as hydrogen bonds and van der Waal interactions getting weaker or stronger, and not from changes in chemical bonds between atoms in the same compound. For example, for ice to melt, the water molecules must obtain enough energy to overcome hydrogen bonding and slip past one another.

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