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I was recently assigned a lab where I was to observe several properties of the chemicals Acetone and Glycerol then use my observations to predict their overall Intermolecular Force strength.

The properties I observed were:

Surface Tension: Here, I found that Acetone had a much higher surface tension than Glycerol. (I tested this by seeing how many drops of each substance would stay on a penny: Acetone had 19 and Glycerol had 13)

Viscosity: Here, I found that Glycerol had a much higher viscosity than Acetone. (I did this by dropping a penny through a 500mL graduated cylinder: Took 0.4 seconds for Acetone and 5ish seconds for Glycerol)

Boiling Point: Researching online, I found that Glycerol had a much higher boiling point than Acetone.

Glycerol also took much longer than Acetone to evaporate.

However, this seems to be conflicting evidence. I have learned that a higher surface tension is associated with overall stronger IMFs (suggesting that Acetone has stronger IMFs), but the other pieces of evidence seem to suggest that Glycerol has stronger IMFs.

My question is, can anybody tell me if Acetone's IMFs really are stronger than Glycerol, or is it the other way around? Additionally, if any of my experimental results seem wrong, can somebody please point them out?

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  • $\begingroup$ Surface tension test seems doubtful. I would rather check, how many drops is needed for 1 mL ( or other arbitrary volume ), corrected for density.. $\endgroup$ – Poutnik Nov 4 '20 at 7:05
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So the intermolecular forces would be stronger in glycerol then in acetone. Glycerol can form hydrogen bonds while acetone is not very polar and can’t significantly form h bonds with itself.

The surface tension for glycerol is 63.4 $\frac{mN}{m}$ while acetone is 25.2 $ \frac{mN}{m}$ (both @ 20 C)

I supposed the error in your experiment arises from using pipette to determine the amount of material on the coin. Unless your using very precise pipettes, counting drops isn’t necessarily the best way to quantify the amount of material added. Additionally the density of glycerol is higher then acetone which needs to be accounted for in the test.

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