What determines a substance's viscosity?

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Discussion Overview

The discussion centers on the factors that determine a substance's viscosity, exploring various physical parameters, molecular patterns, and the influence of temperature and intermolecular forces. The scope includes theoretical and conceptual aspects of viscosity.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions whether viscosity is determined by molecular patterns or other factors.
  • Another participant suggests that viscosity is related to several physical parameters and ultimately to quantum mechanics concepts, though specific details are not recalled.
  • A participant notes that viscosity generally decreases with increasing temperature, using glass as an example to illustrate this point.
  • It is mentioned that larger molecules tend to have higher viscosities compared to smaller analogous molecules, with propanol, ethanol, and methanol cited as examples.
  • Another claim is made that the strength of intermolecular bonds is a key determinant of viscosity, with stronger bonds leading to higher viscosity.
  • Additional factors influencing viscosity, such as temperature, pressure, and state, are acknowledged but not elaborated upon.

Areas of Agreement / Disagreement

Participants express various views on the determinants of viscosity, with no consensus reached on a singular explanation. Multiple competing factors and models are presented, indicating an unresolved discussion.

Contextual Notes

Some assumptions about the relationship between molecular size and viscosity, as well as the influence of temperature and intermolecular forces, remain unexamined. The discussion does not clarify the specific quantum mechanics concepts mentioned.

The P-manator
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What determines a substance's viscosity? Is it a molecular pattern or something of the sort?
 
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It's related several physical parameters, and thus, ultimately to some quantum mechanics concepts, I don't remember the exact one's off the top of my head.
 
In general, as temperature increases for a given substance, viscosity decreases. A great example is glass. At high temperatures when it is workable, glass has a relatively low viscocity but at room temperature it's viscosity is huge (something around the area of 10^35 poise IIRC).

Larger molecules usually have higher viscosity's than analogous smaller molecules. For example, propanol's viscocity is greater than ethanol's which is greater than methanol's.
 
Generally, the strength of a substance's intermolecular bonds determines its viscosity.
The stronger these bonds are, the more viscuous your substance will likely be.

(Other factors include temperature, pressure, state, etc...)
 

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