Intermolecular Forces:

Inter molecular forces is attractive or repulsive forces that occur between all atoms and molecules.Inter molecular forces are weaker forces than the forces associated with chemical bonding. They play an important role in deciding the physical properties of solids, liquids and gases. It also plays an important role in three dimensional arrangements of molecules.

Attractive forces between the molecules are of four types. 

• Ionic forces
• Dipole forces
• Hydrogen bonding
• Induced dipole forces 

Electrostatic inter action or ionic forces:

When a compound is formed between a metal and a non meta , the metal donates its electron to the non mental there by there will be positive metallic ion and negative non metallic ion. They are held together by the strong electro static force of attraction. Tit needs lot of energy to break this force. So the boiling point and melting point of the electrovalent compound will be higher.

The relationship between pressure, volume and temperature of a gas is due to the attractive or repulsive forces between the molecules.The molecules are closely packed in a solid. The inter molecular space is more ibn gases than liquids.

Dipole forces:

Two types of covalent bonds are polar bonding and non polar bonding.

Dipole means having two poles. One due to the pole will have partial positive charge and other will have partial negative charge. For example in hydrogen chloride though it is covalent compound one electron is shared unequally. So H will be positive and Cl will be negative.  

In non polar bonding there will be equal share of electrons there by there will not be any partial charges.

Hydrogen bonding:

Hydrogen bond is the attractive force between the hydrogen attached to the electro negative atom of one molecule and a electro negative atom of different molecule.This will be a weak force.

When an ion or a dipole induces a dipole in a neutral atom or molecule is known as induced dipole forces.The pressure gas is due to the bombardment of the gas molecules on the walls of the container.