STATES OF MATTER-II-LIQUIDS
KEY POINTS:
1. Boiling Point:
The temperature at which the vapour pressure of a liquid becomes equal to the external pressure is called the boiling point of the liquid.
2. Dipole:
The partial separation of charges on a bond between two atoms is called a dipole.
3. Dipole-Dipole forces:
The attractive forces between the positive end of one polar molecule and the negative end of another polar molecule are called dipole-dipole forces.
4. Evaporation:
The spontaneous change of a liquid into its vapours at a given temperature is called evaporation.
5. Viscosity:
The resistance to flow is due to the internal friction between the layers of the molecules.
6. Surface tension:
Force in Newton acting at a right angle on the unit length of a surface of a liquid is called surface tension.
7. Hydrogen bonding:
Hydrogen bonding is the electrostatic force of attraction between the hydrogen atom (bounded to a small highly electronegative atom) of one polar molecule and the electronegative atom of another molecule.
8. Intermolecular forces:
The attractive forces that exist between individual particles i.e. atoms, ions, and molecules.
9. Ion dipole interactions:
The electrostatic forces of attraction between an ion (positive or negative) and the polar molecules of the solvent.
10. Liquid crystal:
It is an intermediate stage of a crystalline substance that exists between two temperatures i.e. the melting temperature and the clearing temperature.
11. London dispersion forces:
The attractive forces between the instantaneous dipole and an induced dipole are called London dispersion forces.
12. Polarizability:
Polarizability is the quantitative measurement of the extent to which the electronic cloud polarizes i.e. separation of charges.
13. Vaccum distillation:
It is the process of heating the liquid under reduced pressure to change it into vapours at a lower temperature and then condensing the vapors to a liquid.