gas

[ohsmurfyea]

How come a decrease in temperature of a gas in a closed container will lead to increased attraction between gas molecules?? Thnx.

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[muchomaas]

I don't know for sure, but couldn't it be because as temperature goes down a gas becomes more like a liquid and liquids experience more interomolecular forces than gases?

 

[FuSoYa]

I think it has to do with the fact that kinetic energy and temperature are directly related. Molecular collisions are repulsive, so if this is decreased, then the attractive forces between molecules goes up. I think... there may be more to it than this.

 

[LeftyUM]

My take on it is that as you decrease the temperature, time of contact with other molecules increases, since they arent moving as fast. Therefore forces tend to occur more often within these molecules. Also I dont know if this has anything to do with it, but how about Le Chateleir's principle. Lowering temperature drives a system to release energy, to return to equilibrium. Making bonds releases energy, so maybe that can happen to try to offset the lowering of temperature. Just my go at it.

 

[phospho]

My take on it is that as you decrease the temperature, time of contact with other molecules increases, since they arent moving as fast. Therefore forces tend to occur more often within these molecules.

i agree

 

[dualityim]

The idea that decreasing temperature results in increased molecular attraction is likely based on the van der waal approximation, which is often incorrect in real life situations (though some test prep companies treat it as infallible). In reality, some gas particles are attractive while others are repulsive (i.e. water vs. hydrogen). To really answer this question, you would have to look at the virial equation - some gases may have smaller or larger compressibility factors than ideal gases, and the strength of intermolecular forces (attractive and repulsive) is more dependant on the pressure than the termperature.
I seriously doubt you would see a question like this on the actual MCAT.l