Types of Intermolecular Forces - Unit 2 Flashcards
What is an intermolecular force?
Intermolecular forces are weak electrostatic attractions that exist between molecules
What are the 2 types of intermolecular forces?
- Vander Waal’s Forces
- Dipole-Dipole
- Dispersion - Hydrogen Bonding
What are Dipole-Dipole Forces?
Dipole-dipole forces only occur between permanent polar molecules
These forces result from the attraction between positive end of a polar molecule and the negative end of another polar molecule
Dipole-Dipole forces strength?
Dipole-Dipole forces are relatively weak since the partial positive and negative charges on the molecules are small
What happens to Dipole-Dipole with polarity?
The higher the polarity of the molecules, the higher the Dipole-Dipole forces will be
Dipole-Dipole: Melting and Boiling points
A substance that contains a stronger Dipole-Dipole force has a higher melting and boiling point
What are Dispersion forces?
These are the weakest intermolecular forces
The dispersion force is the electrostatic attraction between the positive temporary dipole of an atom and the negative induced dipole on a neighboring atom
How do dispersion forces cause temporary dipole?
They are the result of the constant movement of electrons, this can cause temporary dipole moments as there could be more on one side than another at some points
Are dispersion forces always present?
Dispersion forces are always present, regardless of polarity
What molecules tend to have stronger dispersion forces?
Molecules that form long chains will tend to have stronger dispersion forces
This is because as the molecules get longer, the contact between molecules increases, which increases the dispersion forces
When are dispersion forces approximately equal?
For molecules with comparable molecular sizes and shapes, dispersion forces are approximately equal
When does the strength of Dipole-Dipole forces increase?
The strength of Dipole-Dipole forces increases with the polarity of molecules
The Vander Waal/s forces between molecule are stronger if?
- the molecular size is larger
- the contact surface area between the molecules is greater
What are hydrogen bonds?
A strong dipole-dipole force
When do hydrogen bonds occur?
Only occur between highly polar molecules in which a hydrogen atom is covalently bonded to an oxygen, nitrogen or fluorine atom
Hydrogen bonds are FON
