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:
▪ the temperature at which a liquid change into vapor
▪ the higher the temperature needed to boil a liquid → stronger attractive forces (IMF)
▪ the resistance to flow:
▪ the higher the viscosity → stronger attractive forces (IMF)
▪ 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)
Intermolecular Forces (IMF) are the attractive forces between 2 molecules.
▪ strongest IMF
▪ deals with the attraction between an ion and a polar compound.
• Hydrogen Bonding
|Boiling Point (oC)||Surface Tension (J/m2)||Viscosity (kg/m s)|
|Water, H2O||100||7.3 10 - 2||0.9 10 - 3|
|Ethanol, CH3CH2OH||78||2.3 10 - 2||1.1 10 - 3|
|Propanol, CH3CH2CH2OH||97||2.4 10 - 2||2.2 10 - 3|
|n-Butanol, CH3CH2CH2CH2OH||117||2.6 10 - 2||2.6 10 - 3|
|Ethylene glycol, HOCH2CH2OH||197||4.8 10 - 2||26 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.