Intermolecular Forces Flashcards
What are dipole-dipole forces?
Forces between polar molecules with permanent dipoles
Do dipole-dipole forces cancel eachother out?
Sometimes but can also not cancel
How do the dipole-dipole forces work?
They are attracted to the opposite charge so will always flip to attract eachother.
What are van der Waals?
Weak electrostatic forces of attraction
How do van der Waals work?
Electrons can be anywhere in a structure
Distribution of charge is always changing
This causes induced dipoles which change constantly
The new dipoles will be attracted to the old dipoles
These are van der Waals
How do the strength of van der Waals change?
Larger mass = stronger van der Waals
Because the dipoles are caused by the changing electron cloud so the more electrons the larger the instantaneous dipole
What is hydrogen bonding?
Special type of imf
A H + ion between two electronegative atoms
What conditions are required for H bonding?
- A hydrogen atom bonded to either N,O,F
-A very electronegative atom with a lone pair of electrons
What are the trend in boiling points with the different types of attraction/bonds?
Van der Waals < Dipole - Dipole < Hydrogen bonding < Covalent bonding
Why is ice less dense than water?
Water in liquid state causes H bonds to break and reform
When frozen the bonds are held in place apart from eachother
This keeps the ice at a set density which is less than water
Where are H bonds found?
Proteins- H bonds are weaker than covalent bonds so proteins can be modified
DNA
