Why are non-polar molecules attracted to each other?

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In summary, polar molecules bond with each other, while non-polar molecules bond with each other. This is due to the different energy systems that they occupy.
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Hammad Shahid
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Okay guys I have a question that does not make sense to me.
My teachers, and even the chem and bio textbooks, have often said that polar molecules bond with each other, and non-polar molecules bond with each other.

I do get why polar molecules can form bonds, which is due to the e- arrangement, allowing for uneven spread of e-.

However, why do non-polar molecules bond with each other? Ofcourse the explanation is temporary dipoles, but all molecules exhibit that.
So why would, let's say, CH4 (l) mix with itself better than water? (Not considering molecular size)
Yea it's not polar so it mainly forms LDF w/ H2O, but it only forms LDF with itself too. And if anything, it should form stronger bonds with H2O because H2O at least exhibits polarity, and the C-H bond is not super un-polar, so a CH4-H2O bond would be more dipole-dipole than a CH4-CH4. Unless I am wrong in something I have stated (in which case please correct me).

So guys what's the explanation for this?
 
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  • #2
Simple answer: they don't bond.

Longer answer: in the mixture of polar and non-polar molecules the lowest energy system will have non-polar molecules combined, as it allows polar molecules to make more bonds between them (less "molecule surface" is lost to contact with non-polar molecules). It doesn't mean non-polar molecules bond, but it looks as if they did.
 
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Hammad Shahid said:
My teachers, and even the chem and bio textbooks, have often said that polar molecules bond with each other, and non-polar molecules bond with each other.
This is, unfortunately, a common but misleading way to put things. If you consider the interaction of water molecules and oil molecules, you will find that the attraction between a water and an oil molecule is greater than the attrition between two oil molecules. The reason that water and oil separate is that the attraction of two water molecules is so much greater that separation is a lower energy situation.

Looks like @Borek beat me to it...
 
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  • #4
Makes sense thanks guys.
 

1. Why are non-polar molecules attracted to each other?

Non-polar molecules are attracted to each other due to the presence of weak intermolecular forces called Van der Waals forces. These forces arise due to temporary dipoles that occur when the electrons in a molecule are unevenly distributed, causing a slight imbalance in charge. The temporary dipoles of one molecule can induce a temporary dipole in a neighboring molecule, resulting in an attractive force between the two.

2. How do Van der Waals forces allow non-polar molecules to attract each other?

Van der Waals forces, specifically London dispersion forces, are responsible for the attraction between non-polar molecules. These forces arise due to temporary dipoles that occur when the electrons in a molecule are unevenly distributed. This temporary dipole can induce a dipole in a neighboring molecule, resulting in an attractive force between the two.

3. Can non-polar molecules form hydrogen bonds with each other?

No, non-polar molecules cannot form hydrogen bonds with each other. Hydrogen bonds occur between a hydrogen atom and a highly electronegative atom, such as oxygen or nitrogen. Non-polar molecules do not have the necessary polar bonds for hydrogen bonding to occur.

4. What other factors can influence the attraction between non-polar molecules?

The strength of Van der Waals forces between non-polar molecules can also be influenced by factors such as the size and shape of the molecules, as well as the distance between them. Larger molecules tend to have stronger Van der Waals forces, and closer proximity between molecules can increase the strength of the attraction.

5. How do non-polar molecules interact with polar molecules?

Non-polar molecules can interact with polar molecules through London dispersion forces. Even though polar molecules have permanent dipoles, they can still experience temporary dipoles due to the constant movement of electrons. These temporary dipoles can induce a dipole in a nearby non-polar molecule, resulting in an attraction between the two.

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