CBSE Class 11 Chemistry States Of Matter Notes Set 02

CBSE Class 11 Chemistry Notes - States of matter. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations. For more study material for Chemistry please click here - CBSE class 11 chemistry ncert solutions.

Subject: Chemistry

Class: XI

Chapter: States of matter

Top concepts

1. Intermolecular forces are the forces of attraction and repulsion between interacting particles (atoms and molecules).

2. Attractive intermolecular forces are known as van der Waals forces which include dispersion forces or London forces, dipole – dipole forces, and dipole – induced dipole forces.

3. Dispersion forces or London forces exist between neutral atoms like that of noble gases or non – polar molecules like O₂, N₂, H₂ etc. Magnitude of dispersion forces depends on the polarisability of the neutral atom or molecule.

4. Dipole – Dipole forces occur between the molecules have permanent dipole such as HCl, NH₃, H₂O etc.

5. Dipole – Induced Dipole forces operate between the polar molecule having permanent dipole and the molecule having no permanent dipole.

6. Hydrogen bond is a special case of dipole-dipole interaction. When hydrogen atom is bonded to atoms of highly electronegative elements such as fluorine, oxygen or nitrogen, hydrogen atom forms a weak bond with the electronegative atom of the other molecule. This weak bond is called hydrogen bond.

7. Thermal energy is the energy of a body arising from motion of its atoms or molecules.

8. Three states of matter are the result of balance between intermolecular forces and the thermal energy of the molecules.

9. Predominance of molecular interactions result into change of gases to liquid to solid state while predominance of thermal energy results into change of solid to liquid to gas.

10.Physical properties of gas

• Gases are highly compressible

• Gases exert pressure equally in all directions

• Gases have density much lower than the solids and liquids

• Gases do not have definite volume and the shape. They assume volume and shape of the container

• Gases mix evenly and completely in all proportions without any mechanical aid. 

11.According to Boyle’s law at constant temperature, the pressure of a fixed amount (i.e., number of moles n) of gas varies inversely with its volume Mathematically, it is written as 

p œ1/V, (n,T are constant

pV= k₁ (constant) 

Value of k depends on amount of gas and temperature and units in which p and V are expressed.

12. Boyle’s law expresses in a quantitative manner that gases are compressible because when a given mass of a gas is compressed, the same number of molecules occupy a smaller space.

13.According to Charles’ Law at constant pressure, the volume of fixed mass of a gas is directly proportional to absolute temperature.  Mathematically, it is written as 

VœT(p,N are constant)

V/T=k²(constant) 

Value of k₂ depends on amount of gas and pressure and units in which volume V is expressed.

14. The lowest hypothetical or imaginary temperature at which gases are supposed to occupy zero volume is called Absolute zero.

15.According to Gay Lussac’s Law at constant volume, pressure of a fixed amount of a gas varies directly with the  emperature. Mathematically, it is written as

pœT(n,V are constant)

or P/T=k₃ (constant)

16. Standard temperature and pressure means 273.15 K (0^oC) temperature and 1 bar (i.e., exactly 10⁵ Pascal) pressure.

17. According to Avogadro Law equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules. Mathematically, it is written as

Vœn(p,T are constant)

œV/n=k₄  (constant)

18.A gas that follows Boyle’s Law, Charles’ law and Avogadro law strictly is called an ideal gas.

19. Ideal Gas Equation : pV = nRT R is called gas constant. It is same for all gases. Therefore it is also called Universal Gas Constant. 

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