Intermolecular forces Flashcards
How do intermolecular forces play a role in how a molecule behaves?
Influence physical properties, specifically melting and boiling points and solubilities
What are the 4 types of intermolecular forces?
ionic, dipole-dipole, H-bonds, Van der Waals
Why are intermolecular forces additive?
They’re weak individually, but add up. The more there are, the stronger they are
What is the strongest type of intermolecular force?
Ionic
What is the weakest type of intermolecular force?
Van der Waals
What is a dipole-dipole interaction?
Attraction or repulsion between dipole moments on polar molecules
When would dipole-dipole interactions be attractive?
When the partial positive and partial negative ends of two polar molecules approach each other
When would dipole-dipole interactions be repulsive?
When both partial positive or both partial negative ends of the polar molecules approach each other
Are attractive or repulsive dipole-dipole interactions more common? Why?
Attractive. Molecules will naturally orient themselves with the opposite partial charges facing each other, resulting in a net attractive force
What are hydrogen bonds?
A stronger form of dipole-dipole interactions, formed from an H on an OH or an NH being strongly attracted to the lone pair on O or N
What two functional groups can participate in H-bonds?
OH and NH
What types of molecules are Van der Waals forces found in?
All molecules
What creates Van der Waals forces?
Temporary dipole-dipole interactions formed from other molecules nearby
What intermolecular force is the main attractive force in hydrophobic molecules?
Van der Waals
Why do molecules with less branching have higher melting points than molecules with more branching? What intermolecular force is responsible for this?
Higher surface area and more surface contact. Van der Waals forces are responsible for this
