Why is glycerol much thicker than ethylene glycol, which in turn is much thicker than ethanol?

Question

Why is glycerol much thicker than ethylene glycol, which in turn is much thicker than ethanol?

Answer 1

I'm guessing when you say "thickness" you're referring to the viscosity of the three liquids?

I don't quite know all the factors that affect the viscosity of a fluid but I do know that intermolecular forces are partly responsible for the viscosity of fluids.

Ethylene glycol has two polar -OH groups capable of forming hydrogen bonds however Glycerol has three polar -OH groups capable of forming hydrogen bonds so it has stronger intermolecular forces than ethylene glycol. The fact that glycerol has stronger van der waals forces because the molecule has more electrons than ethylene glycol. The stronger attractive force between molecules is part of the reason why glycerol is more viscous than ethylene glycol. Ethanol is the least viscous of the three because it has only one -OH group and a lower number of electrons per molecule so the intermolecular forces in ethanol are weaker than in the other two.

That should partly explain their different viscosities(thicknesses) but like I said, there are more factors that I don't know enough about to explain. Some liquid molecules tangle together and that also plays some part in their viscosity.

Answer 2

Thicker? Thicker...? Hmmm...You probably mean 'viscous'...well it would be something to do with molecules hanging together or not...forming stronger bonds with those in their immediate vicinity...polar bonds and Van der Waals forces spring to ming and OBVIOUSLY molecular shape; look up and compare the different,respective structures...