2nd Lecture on States of Matter Chemistry Part II 11th Standard by Rizwana Mohammed

1. The Malegaon High School & Jr. College
Malegaon, (Nashik), 423203
2nd Lecture on States of Matter
Chemistry Part II, 11th Science
By
Rizwana Mohammad

2. Intermolecular forces:
iv. London dispersion forces:
• In case of non polar molecules and inert gases, only dispersion forces
exist.
• These forces are also called as London forces or van der Waals forces.
• All atoms and molecules experience London dispersion forces, which
result from the motion of electrons.
• The interaction between atoms or nonpolar molecules is through
dispersion forces which depend on polarizability of the atom or
molecule.
• Polarizability is the ease with which the arrangement of electrons in
the atom or molecule can be disturbed.
• Dispersion forces are attractive forces that originate as a result of
instantaneous dipoles induced in atoms or molecules.

3. v. Hydrogen bonding:
• The electrostatic force of attraction between positively polarised
hydrogen atom of one molecule and a highly electronegative atom of
other molecule is called as hydrogen bond.
• Hydrogen bond is denoted by (….) dotted line.
• There are two types of hydrogen bond
i. Intramolecular hydrogen bond:
Hydrogen bonds within the same molecule is intramolecular hydrogen
bond e.g. ethylene glycol
ii. Intermolecular hydrogen bond:
A hydrogen bond present between two like or unlike molecules.

4. H bonding and boiling point:
• More energy is required to break the H bond.
• Therefore, boiling point is more in case of liquid molecules containing
H-bond.
Intermolecular forces and thermal energy:
• Thermal energy arises due to movement of particles.
• It is directly proportional to temperature,
Thermal energy ∝
1
Intermolecular force