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baggier t1_j2tab8w wrote

Reply to comment by Duros001 in Molecularly, what make pine pitch sticky? by orangegore

I would broadly agree except on the density bit. Tar is not much denser than water but the key attribute is the size of the molecules. Larger molecules have more area to interact with each other, resulting in more attraction and slower motion (e.g. higher viscosity). Tar molecules are about 10-20 times bigger than water.

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Duros001 t1_j2vp2y3 wrote

True, but the interstitial pressure of a compound or emulsion is also dependent of the presence of micelles, as I presume tar is made up of various length hydrocarbons, some of which will be relatively short chain oils, among a soup of other organic compounds

Plus there are several types of “Tar” Pitch/Coal Tar are even lumped together on databases: 1.1-1.4 g/cm^3 (https://echa.europa.eu/registration-dossier/-/registered-dossier/15300/4/5) The water content, hydrocarbon lengths etc will depend on so many factors, temp it was refined at, local or actual source of “tar” (pine, coal, peat etc)

It’s almost like we’re trying to generalise a cake mix, made by thousands of different bakers, it contains mostly the same stuff, but will cook totally different :)

Edit: But yes, you are correct that viscosity is greatly affected by particle/molecular size :D thanks for the correction :)

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