Intermolecular forces Flashcards
What is a dipole-dipole force?
Forces of attraction between the positive end of one polar molecule and the negative end of another
What is hydrogen bonding?
Hydrogen bonded to N/O/F
How do you represent a hydrogen bond?
Dotted line between hydrogen atom and lone pair of the other atom (show partial charges)
What are Van der Waals forces?
Constantly moving electron cloud causes an uneven distribution of electrons, creating a temporary dipole. The slightly negative side of the molecule will repel the electrons in a nearby molecule, inducing a temporary dipole . The slightly negative side of one molecule will be attracted to the slightly positive side of another
What happens when you melt molecular solids?
The lattice breaks down, but molecules still experience intermolecular forces to nearby molecules, but are weaker so molecules move around in the substance
What happens when you boil melted molecular solids?
Molecules move further apart, so intermolecular forces have become so weak to the point you ignore them
What affects the strength of Van der Waals forces?
Number of electrons
What gives molecules stronger Van der Waals forces (higher melting and boiling points)?
If the molecule has more electrons
How do you compare melting and boiling points of molecules?
Compare intermolecular forces present and the strengths of them
‘Like dissolves like’ rule?
Polar molecules dissolve in polar substances
Nonpolar molecules dissolve in nonpolar substances
Why is ice less dense than water?
In ice, the hydrogen bonds hold the water molecules further away from each other. This results in large gaps in the lattice called an open lattice structure, and the gaps between the water molecules in ice increase its volume.
