Intermolecular Bonds

Intermolecular bonds are weak bonds between molecules.
For example, when water turns to ice, its molecules bond together in a lattice.
When ice melts, the intermolecular bonds break, to form lone water molecules.
The structure of water molecules doesn't change, its lattice does.
Lattices formed by intermolecular bonds can be broken easily through physical means.

The Types of Intermolecular Bonds

There are three kinds of weak bonds, also called intermolecular forces.
Hydrogen bonds, which are the strongest of the three.
Dipole-dipole forces.
And London dispersion forces, which are the weakest.
These bonds are all weaker than metallic bonds (which are the weakest of the strong bonds, slightly weaker than covalent and ionic bonds) and can be broken with relative ease.

The partial charges of polar molecules attract one another.
The negative partial charge of a polar molecule attracts the positive partial charge of another dipole molecule.
The bond is formed between polar molecules and is called a dipole-dipole bond. This bond is shown as the formulae of both molecules, connected by a dotted line.
Dipole-dipole forces are formed between polar molecules.

A hydrogen bond is a special case of a dipole-dipole bond.
It is stronger than a dipole-dipole bond.
It is also the strongest type of intermolecular forces.
It occurs if some of the most electronegative atoms bond with hydrogen atoms from another molecule.
Generally Fluorine, Oxygen or Nitrogen as they are the three most electronegative elements.
For example F-H, N-H or O-H chains, where the electronegative atoms bond with the hydrogen from the other molecules, in addition to the covalent bond they already have with hydrogen.
For example water molecules form hydrogen bonds between themselves.

There are London dispersion forces between nonpolar molecules and unreactive atoms.
Dispersion forces are formed by the interaction between instantaneous dipoles (meaning they become temporarily polar).
They occur when the valence electrons of an atom happen to be in one spot, causing a temporary partial charge.
The bond requires very little energy to overcome however.
For example as H20 molecules are liquid in room temperature because they have a hydrogen bond, which is stronger than the London dispersion bond oxygen molecules have when not in a compound.

Molecular lattice is formed by bonds between molecules.
Polar molecules form a polar molecular lattice held together by dipole-dipole bonds or hydrogen bonds.
Nonpolar molecules arrange themselves in a nonpolar molecular lattice, where dispersion forces act between the molecules.
An amorphous substance does not have a regular molecular lattice or a precise melting point.
Amorphous substances possess no order and appear more as clumps.