Problem: The boiling points, surface tensions, and viscosities of water and several alcohols are as follows:Boiling Point (oC)Surface Tension (J/m2)Viscosity (kg/m s)Water, H2O1007.3 10 - 20.9 10 - 3Ethanol, CH3CH2OH782.3 10 - 21.1 10 - 3Propanol, CH3CH2CH2OH972.4 10 - 22.2 10 - 3n-Butanol, CH3CH2CH2CH2OH1172.6 10 - 22.6 10 - 3Ethylene glycol, HOCH2CH2OH1974.8 10 - 226 10 - 3For ethanol, propanol, and n-butanol the boiling points, surface tensions, and viscosities all increase. What is the reason for this increase?

FREE Expert Solution

We’re asked to determine the reason for the increase in the boiling points, surface tensions, and viscosities for ethanol, propanol, and n-butanol based on the given data. 


Recall that the following physical properties are affected by the intermolecular forces (IMF) present in molecules:


Boiling Point

 the temperature at which a liquid change into vapor 

the higher the temperature needed to boil a liquid  stronger attractive forces (IMF)

  • (↑ BP)   stronger IMF ( IMF)
  • (VP)  weaker IMF (↓ IMF)


Viscosity

 the resistance to flow: 

  • ↓ viscosity flows freely 
  • ↑ viscosity: restricted flow (stronger IMF)

the higher the viscosity  stronger attractive forces (IMF)

  • (↑Viscosity)   stronger IMF ( IMF)
  • (↓Viscosity weaker IMF (↓ IMF)


Surface tension

 the property of the surface of a liquid that allows it to resist an external force (instead of breaking apart into smaller droplets) due to attractive forces (IMF) between molecules

the higher the surface tension  stronger attractive forces (IMF)

  • (↑ST)   stronger IMF ( IMF)
  • (↓ST weaker IMF (↓ IMF)


Intermolecular Forces (IMF) are the attractive forces between 2 molecules.

Ion-dipole

strongest IMF
▪ deals with the attraction between an ion and a polar compound.

 Hydrogen Bonding

View Complete Written Solution
Problem Details
The boiling points, surface tensions, and viscosities of water and several alcohols are as follows:



Boiling Point (oC)Surface Tension (J/m2)Viscosity (kg/m s)
Water, H2O1007.3 10 - 20.9 10 - 3
Ethanol, CH3CH2OH782.3 10 - 21.1 10 - 3
Propanol, CH3CH2CH2OH972.4 10 - 22.2 10 - 3
n-Butanol, CH3CH2CH2CH2OH1172.6 10 - 22.6 10 - 3
Ethylene glycol, HOCH2CH2OH1974.8 10 - 226 10 - 3


For ethanol, propanol, and n-butanol the boiling points, surface tensions, and viscosities all increase. What is the reason for this increase?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Intermolecular Forces and Physical Properties concept. If you need more Intermolecular Forces and Physical Properties practice, you can also practice Intermolecular Forces and Physical Properties practice problems.