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States of Matter - Gases, Liquids & Solids Class 11 Notes Chemistry

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? On the basis of nature of intermolecular forces/molecular interactions,
matter exists in three physical states : solid, liquid and gas.
? Intermolecular forces are the forces of attraction or repulsion between
interacting particles (atoms and molecules). Attractive/repulsive
intermolecular forces are known as van der Waal’s forces.
Different	types	of	van	der	 W aal’ s	forces	are	:
(a) Disperson forces or London forces : The interaction which is present
between two non polar molecules for example force between : noble gases.
(b) Dipole-dipole forces : The interaction which is present between
molecules having permanent dipoles i.e., between polar molecules, for
example NH
3
, HCl etc.
(c) Dipole-induced dipole forces : The interaction which is present
between a polar and non polar molecule.
? Boyle ’s law : 	 At	 constant	 temperature,	 the	 pressure	 of	 a	 fixed	 amount	 of
gas, varies inversly with volume.
P a 
P
1
V
1
 = P
2
V
2
 [At constant temperature]
? Charle ’s law : At	 constant	 pressure,	 the	 volume	 of	 a	 fixed	 mass	 of	 gas	 is
directly proportional to its absolute temperature.
V a T
 = [At constant pressure (p) and n]
Page 2


? On the basis of nature of intermolecular forces/molecular interactions,
matter exists in three physical states : solid, liquid and gas.
? Intermolecular forces are the forces of attraction or repulsion between
interacting particles (atoms and molecules). Attractive/repulsive
intermolecular forces are known as van der Waal’s forces.
Different	types	of	van	der	 W aal’ s	forces	are	:
(a) Disperson forces or London forces : The interaction which is present
between two non polar molecules for example force between : noble gases.
(b) Dipole-dipole forces : The interaction which is present between
molecules having permanent dipoles i.e., between polar molecules, for
example NH
3
, HCl etc.
(c) Dipole-induced dipole forces : The interaction which is present
between a polar and non polar molecule.
? Boyle ’s law : 	 At	 constant	 temperature,	 the	 pressure	 of	 a	 fixed	 amount	 of
gas, varies inversly with volume.
P a 
P
1
V
1
 = P
2
V
2
 [At constant temperature]
? Charle ’s law : At	 constant	 pressure,	 the	 volume	 of	 a	 fixed	 mass	 of	 gas	 is
directly proportional to its absolute temperature.
V a T
 = [At constant pressure (p) and n]
? Gay Lussac ’s law : 	 At	 constant	 volume,	 pressure	 of	 a	 fixed	 amount 	 of
gas varies directly with the absolute temperature.
P ? T,  =   [At constant volume (V) and n].
? STP (Standard Temperature and Pressure) : STP means 273.15 K
(0°C) temperature and 1 bar (i.e., exactly 10
5
 Pascal.) Volume occupied
by 1 mole gas at STP = 22.7 L.
If pressure is taken in atm (atmosphere), then the standard molar volume
is 22.4 L.
? Ideal gas equation : PV = nRT
R is universal gas constant.
R = 8.314 JK
–1
 mol
–1
 = 0.0821 L atm mol
–1
 K
–1
 = 0.083 L bar mol
–1
 K
–1
? Combined gas law : = 
? Density and molar mass of a gaseous substance :
M  = 
? Dalton ’s law of partial pressure : Dalton states that the total pressure
exerted by the mixture of non reacting gases is equal to the sum of the
partial pressures of individual gases.
  P
total 
= P
1
 + P
2
 + P
3 
+ ..... [at constant T, V]
  P
1
 = x
1
 × P
Total
 = Here x
1
	is	called	mole 	fractio n	of	the	first	gas.
  P
dry gas
 = P
Total
 – Aqueous tension.
Here aqueous tension is the pressure exerted by water vapours.
? Compressibility factor : The extent of deviation of a real gas from an
ideal behaviour is expressed in terms of compressibility factor, Z =
For ideal gas, Z = 1 at all temperatures and pressures. For real gases, greater
is the deviation in the value of Z from 1, more is the deviation from ideal
behaviour .	 When	 Z	 <	 1,	 the	 gas	 is	 said	 to	 show 	 negat ive	 deviation.	 This
implies that gas is more compressible then expected from ideal behaviour.
When	 Z	 >	 1,	 the	 gas	 is	 said	 to	 show	 positive	 deviation 	 and	 the	 gas	 is	 less
compressible than expected from ideal behaviour.
Page 3


? On the basis of nature of intermolecular forces/molecular interactions,
matter exists in three physical states : solid, liquid and gas.
? Intermolecular forces are the forces of attraction or repulsion between
interacting particles (atoms and molecules). Attractive/repulsive
intermolecular forces are known as van der Waal’s forces.
Different	types	of	van	der	 W aal’ s	forces	are	:
(a) Disperson forces or London forces : The interaction which is present
between two non polar molecules for example force between : noble gases.
(b) Dipole-dipole forces : The interaction which is present between
molecules having permanent dipoles i.e., between polar molecules, for
example NH
3
, HCl etc.
(c) Dipole-induced dipole forces : The interaction which is present
between a polar and non polar molecule.
? Boyle ’s law : 	 At	 constant	 temperature,	 the	 pressure	 of	 a	 fixed	 amount	 of
gas, varies inversly with volume.
P a 
P
1
V
1
 = P
2
V
2
 [At constant temperature]
? Charle ’s law : At	 constant	 pressure,	 the	 volume	 of	 a	 fixed	 mass	 of	 gas	 is
directly proportional to its absolute temperature.
V a T
 = [At constant pressure (p) and n]
? Gay Lussac ’s law : 	 At	 constant	 volume,	 pressure	 of	 a	 fixed	 amount 	 of
gas varies directly with the absolute temperature.
P ? T,  =   [At constant volume (V) and n].
? STP (Standard Temperature and Pressure) : STP means 273.15 K
(0°C) temperature and 1 bar (i.e., exactly 10
5
 Pascal.) Volume occupied
by 1 mole gas at STP = 22.7 L.
If pressure is taken in atm (atmosphere), then the standard molar volume
is 22.4 L.
? Ideal gas equation : PV = nRT
R is universal gas constant.
R = 8.314 JK
–1
 mol
–1
 = 0.0821 L atm mol
–1
 K
–1
 = 0.083 L bar mol
–1
 K
–1
? Combined gas law : = 
? Density and molar mass of a gaseous substance :
M  = 
? Dalton ’s law of partial pressure : Dalton states that the total pressure
exerted by the mixture of non reacting gases is equal to the sum of the
partial pressures of individual gases.
  P
total 
= P
1
 + P
2
 + P
3 
+ ..... [at constant T, V]
  P
1
 = x
1
 × P
Total
 = Here x
1
	is	called	mole 	fractio n	of	the	first	gas.
  P
dry gas
 = P
Total
 – Aqueous tension.
Here aqueous tension is the pressure exerted by water vapours.
? Compressibility factor : The extent of deviation of a real gas from an
ideal behaviour is expressed in terms of compressibility factor, Z =
For ideal gas, Z = 1 at all temperatures and pressures. For real gases, greater
is the deviation in the value of Z from 1, more is the deviation from ideal
behaviour .	 When	 Z	 <	 1,	 the	 gas	 is	 said	 to	 show 	 negat ive	 deviation.	 This
implies that gas is more compressible then expected from ideal behaviour.
When	 Z	 >	 1,	 the	 gas	 is	 said	 to	 show	 positive	 deviation 	 and	 the	 gas	 is	 less
compressible than expected from ideal behaviour.
At ordinary temperatures (T = 273 K), only H
2
 and He show positive 
deviations. However at low temperatures, even these gases show negative 
deviation i.e. ,	 <	 1.	For example ,	 in	 case	 of	 these	 gases,	 if	 T 	 <<	 273	 K,	 
Z 	< 	1.
? Boyle temperature : The temperature at which a real gas behaves like an
ideal gas over an appreciable pressure range is called Boyle temperature
or Boyle point.
? Causes of deviation from ideal behaviour : The following two
assumptions of the kinetic theory of gases are faulty :
(a) The volume occupied by the gas molecules is negligible as compared
to the total volume of the gas.
(b) The forces of attraction or repulsion between the gas molecules are
negligible.
The above assumptions are correct only if the temperature is high and
pressure is low.
van der Waal’s equation :
  = RT for 1 mole of the gas
  = nRT for n moles of the gas
  Here a and b 	are 	constants	called	van	der	 W aal’ s	constants.
? Significance and units of van der Waal’s constants : ‘a ’ 	 gives 	 the 	 idea 	 of
the magnitude of attractive forces among the gas molecules. As correction
in pressure is P = therefore a = (P × V
2
)/n
2
 = atm L
2
 mol
2
.
As correction in volume V = nb, therefore ‘b’ 	 has	 the	 unit	 of	 L 	 mol
–1
.
The near constancy in the volume of b shows that the gas molecules are
incompressible.
? Vapour pressure : The pressure exerted by the vapours of a liquid, when
it is in equilibrium with the liquid surface, at constant temperature.
? Boiling temperature : The temperature at which vapour pressure of a
liquid is equal to the external pressure.
? At 1 atm, boiling temperature is called normal boiling point.
? At 1 bar boiling temperature is called standard boiling point.
Page 4


? On the basis of nature of intermolecular forces/molecular interactions,
matter exists in three physical states : solid, liquid and gas.
? Intermolecular forces are the forces of attraction or repulsion between
interacting particles (atoms and molecules). Attractive/repulsive
intermolecular forces are known as van der Waal’s forces.
Different	types	of	van	der	 W aal’ s	forces	are	:
(a) Disperson forces or London forces : The interaction which is present
between two non polar molecules for example force between : noble gases.
(b) Dipole-dipole forces : The interaction which is present between
molecules having permanent dipoles i.e., between polar molecules, for
example NH
3
, HCl etc.
(c) Dipole-induced dipole forces : The interaction which is present
between a polar and non polar molecule.
? Boyle ’s law : 	 At	 constant	 temperature,	 the	 pressure	 of	 a	 fixed	 amount	 of
gas, varies inversly with volume.
P a 
P
1
V
1
 = P
2
V
2
 [At constant temperature]
? Charle ’s law : At	 constant	 pressure,	 the	 volume	 of	 a	 fixed	 mass	 of	 gas	 is
directly proportional to its absolute temperature.
V a T
 = [At constant pressure (p) and n]
? Gay Lussac ’s law : 	 At	 constant	 volume,	 pressure	 of	 a	 fixed	 amount 	 of
gas varies directly with the absolute temperature.
P ? T,  =   [At constant volume (V) and n].
? STP (Standard Temperature and Pressure) : STP means 273.15 K
(0°C) temperature and 1 bar (i.e., exactly 10
5
 Pascal.) Volume occupied
by 1 mole gas at STP = 22.7 L.
If pressure is taken in atm (atmosphere), then the standard molar volume
is 22.4 L.
? Ideal gas equation : PV = nRT
R is universal gas constant.
R = 8.314 JK
–1
 mol
–1
 = 0.0821 L atm mol
–1
 K
–1
 = 0.083 L bar mol
–1
 K
–1
? Combined gas law : = 
? Density and molar mass of a gaseous substance :
M  = 
? Dalton ’s law of partial pressure : Dalton states that the total pressure
exerted by the mixture of non reacting gases is equal to the sum of the
partial pressures of individual gases.
  P
total 
= P
1
 + P
2
 + P
3 
+ ..... [at constant T, V]
  P
1
 = x
1
 × P
Total
 = Here x
1
	is	called	mole 	fractio n	of	the	first	gas.
  P
dry gas
 = P
Total
 – Aqueous tension.
Here aqueous tension is the pressure exerted by water vapours.
? Compressibility factor : The extent of deviation of a real gas from an
ideal behaviour is expressed in terms of compressibility factor, Z =
For ideal gas, Z = 1 at all temperatures and pressures. For real gases, greater
is the deviation in the value of Z from 1, more is the deviation from ideal
behaviour .	 When	 Z	 <	 1,	 the	 gas	 is	 said	 to	 show 	 negat ive	 deviation.	 This
implies that gas is more compressible then expected from ideal behaviour.
When	 Z	 >	 1,	 the	 gas	 is	 said	 to	 show	 positive	 deviation 	 and	 the	 gas	 is	 less
compressible than expected from ideal behaviour.
At ordinary temperatures (T = 273 K), only H
2
 and He show positive 
deviations. However at low temperatures, even these gases show negative 
deviation i.e. ,	 <	 1.	For example ,	 in	 case	 of	 these	 gases,	 if	 T 	 <<	 273	 K,	 
Z 	< 	1.
? Boyle temperature : The temperature at which a real gas behaves like an
ideal gas over an appreciable pressure range is called Boyle temperature
or Boyle point.
? Causes of deviation from ideal behaviour : The following two
assumptions of the kinetic theory of gases are faulty :
(a) The volume occupied by the gas molecules is negligible as compared
to the total volume of the gas.
(b) The forces of attraction or repulsion between the gas molecules are
negligible.
The above assumptions are correct only if the temperature is high and
pressure is low.
van der Waal’s equation :
  = RT for 1 mole of the gas
  = nRT for n moles of the gas
  Here a and b 	are 	constants	called	van	der	 W aal’ s	constants.
? Significance and units of van der Waal’s constants : ‘a ’ 	 gives 	 the 	 idea 	 of
the magnitude of attractive forces among the gas molecules. As correction
in pressure is P = therefore a = (P × V
2
)/n
2
 = atm L
2
 mol
2
.
As correction in volume V = nb, therefore ‘b’ 	 has	 the	 unit	 of	 L 	 mol
–1
.
The near constancy in the volume of b shows that the gas molecules are
incompressible.
? Vapour pressure : The pressure exerted by the vapours of a liquid, when
it is in equilibrium with the liquid surface, at constant temperature.
? Boiling temperature : The temperature at which vapour pressure of a
liquid is equal to the external pressure.
? At 1 atm, boiling temperature is called normal boiling point.
? At 1 bar boiling temperature is called standard boiling point.
? Vapour pressure of a pure liquid depends upon (i) intermolecular forces,
(ii) Temperature.
? Surface 	 tension	 is	 defined	 as 	 force 	 acting 	 per	 unit	 length 	 perpendicular	 to
the line drawn on the surface. Its units is Nm
–1
.
? Effect of temperature on surface tension : Surface tension decreases with
increase in temperature with the increase in temperature, kinetic energy
of molecules increases. As a result, intermolecular forces decreases and
hence force acting per unit length decreases.
? Viscosity : It 	 is	 defined	 as 	 resistance	 offered	 to	 the 	 flow	 of 	 liquid	 due	 to
internal 	friction 	between	layers	of	fluids	as	they	pass	over	each	other .
F  = ?A. 
  ? is called coefficient of viscosity.
  Effect of temperature on viscosity : Viscosity decrease with increase in 
temperature because with the increase in temperature the average kinetic 
energy increases and the intermolecular forces can be easily overcome.
The Solid State
Crystalline and Amorphous solids
Crystalline solids Amorphous solids
1. They have regular geometry They have irregular geometry
2. They have long range order They have short range order.
3. They have sharp melting point. They have no sharp melting point.
4. They are anisotropic They are isotropic
5. They give clean and smooth surface on
cleavage.
They give irregular cut on cleavage
6. They	have	definite 	heat	of	fusion. They	 do	 not	 have	 definite 	 heat 	 of	
fusion.
7. They are true solids. They are pseudo solids or super 
cooled liquids.
Page 5


? On the basis of nature of intermolecular forces/molecular interactions,
matter exists in three physical states : solid, liquid and gas.
? Intermolecular forces are the forces of attraction or repulsion between
interacting particles (atoms and molecules). Attractive/repulsive
intermolecular forces are known as van der Waal’s forces.
Different	types	of	van	der	 W aal’ s	forces	are	:
(a) Disperson forces or London forces : The interaction which is present
between two non polar molecules for example force between : noble gases.
(b) Dipole-dipole forces : The interaction which is present between
molecules having permanent dipoles i.e., between polar molecules, for
example NH
3
, HCl etc.
(c) Dipole-induced dipole forces : The interaction which is present
between a polar and non polar molecule.
? Boyle ’s law : 	 At	 constant	 temperature,	 the	 pressure	 of	 a	 fixed	 amount	 of
gas, varies inversly with volume.
P a 
P
1
V
1
 = P
2
V
2
 [At constant temperature]
? Charle ’s law : At	 constant	 pressure,	 the	 volume	 of	 a	 fixed	 mass	 of	 gas	 is
directly proportional to its absolute temperature.
V a T
 = [At constant pressure (p) and n]
? Gay Lussac ’s law : 	 At	 constant	 volume,	 pressure	 of	 a	 fixed	 amount 	 of
gas varies directly with the absolute temperature.
P ? T,  =   [At constant volume (V) and n].
? STP (Standard Temperature and Pressure) : STP means 273.15 K
(0°C) temperature and 1 bar (i.e., exactly 10
5
 Pascal.) Volume occupied
by 1 mole gas at STP = 22.7 L.
If pressure is taken in atm (atmosphere), then the standard molar volume
is 22.4 L.
? Ideal gas equation : PV = nRT
R is universal gas constant.
R = 8.314 JK
–1
 mol
–1
 = 0.0821 L atm mol
–1
 K
–1
 = 0.083 L bar mol
–1
 K
–1
? Combined gas law : = 
? Density and molar mass of a gaseous substance :
M  = 
? Dalton ’s law of partial pressure : Dalton states that the total pressure
exerted by the mixture of non reacting gases is equal to the sum of the
partial pressures of individual gases.
  P
total 
= P
1
 + P
2
 + P
3 
+ ..... [at constant T, V]
  P
1
 = x
1
 × P
Total
 = Here x
1
	is	called	mole 	fractio n	of	the	first	gas.
  P
dry gas
 = P
Total
 – Aqueous tension.
Here aqueous tension is the pressure exerted by water vapours.
? Compressibility factor : The extent of deviation of a real gas from an
ideal behaviour is expressed in terms of compressibility factor, Z =
For ideal gas, Z = 1 at all temperatures and pressures. For real gases, greater
is the deviation in the value of Z from 1, more is the deviation from ideal
behaviour .	 When	 Z	 <	 1,	 the	 gas	 is	 said	 to	 show 	 negat ive	 deviation.	 This
implies that gas is more compressible then expected from ideal behaviour.
When	 Z	 >	 1,	 the	 gas	 is	 said	 to	 show	 positive	 deviation 	 and	 the	 gas	 is	 less
compressible than expected from ideal behaviour.
At ordinary temperatures (T = 273 K), only H
2
 and He show positive 
deviations. However at low temperatures, even these gases show negative 
deviation i.e. ,	 <	 1.	For example ,	 in	 case	 of	 these	 gases,	 if	 T 	 <<	 273	 K,	 
Z 	< 	1.
? Boyle temperature : The temperature at which a real gas behaves like an
ideal gas over an appreciable pressure range is called Boyle temperature
or Boyle point.
? Causes of deviation from ideal behaviour : The following two
assumptions of the kinetic theory of gases are faulty :
(a) The volume occupied by the gas molecules is negligible as compared
to the total volume of the gas.
(b) The forces of attraction or repulsion between the gas molecules are
negligible.
The above assumptions are correct only if the temperature is high and
pressure is low.
van der Waal’s equation :
  = RT for 1 mole of the gas
  = nRT for n moles of the gas
  Here a and b 	are 	constants	called	van	der	 W aal’ s	constants.
? Significance and units of van der Waal’s constants : ‘a ’ 	 gives 	 the 	 idea 	 of
the magnitude of attractive forces among the gas molecules. As correction
in pressure is P = therefore a = (P × V
2
)/n
2
 = atm L
2
 mol
2
.
As correction in volume V = nb, therefore ‘b’ 	 has	 the	 unit	 of	 L 	 mol
–1
.
The near constancy in the volume of b shows that the gas molecules are
incompressible.
? Vapour pressure : The pressure exerted by the vapours of a liquid, when
it is in equilibrium with the liquid surface, at constant temperature.
? Boiling temperature : The temperature at which vapour pressure of a
liquid is equal to the external pressure.
? At 1 atm, boiling temperature is called normal boiling point.
? At 1 bar boiling temperature is called standard boiling point.
? Vapour pressure of a pure liquid depends upon (i) intermolecular forces,
(ii) Temperature.
? Surface 	 tension	 is	 defined	 as 	 force 	 acting 	 per	 unit	 length 	 perpendicular	 to
the line drawn on the surface. Its units is Nm
–1
.
? Effect of temperature on surface tension : Surface tension decreases with
increase in temperature with the increase in temperature, kinetic energy
of molecules increases. As a result, intermolecular forces decreases and
hence force acting per unit length decreases.
? Viscosity : It 	 is	 defined	 as 	 resistance	 offered	 to	 the 	 flow	 of 	 liquid	 due	 to
internal 	friction 	between	layers	of	fluids	as	they	pass	over	each	other .
F  = ?A. 
  ? is called coefficient of viscosity.
  Effect of temperature on viscosity : Viscosity decrease with increase in 
temperature because with the increase in temperature the average kinetic 
energy increases and the intermolecular forces can be easily overcome.
The Solid State
Crystalline and Amorphous solids
Crystalline solids Amorphous solids
1. They have regular geometry They have irregular geometry
2. They have long range order They have short range order.
3. They have sharp melting point. They have no sharp melting point.
4. They are anisotropic They are isotropic
5. They give clean and smooth surface on
cleavage.
They give irregular cut on cleavage
6. They	have	definite 	heat	of	fusion. They	 do	 not	 have	 definite 	 heat 	 of	
fusion.
7. They are true solids. They are pseudo solids or super 
cooled liquids.
Anisotropic : Solids	 which	 have	 different 	 values	 of	 their 	 physical	 properties	 such 	
as	refractive 	index,	conductivity	etc.	in	different 	directions.
Isotropic : Solids which have same values of their physical properties such as 
refractive	index,	conductivity	etc.	in	different 	directions.
Classification of crystalline solids:
Space lattice (Crystal lattice)
  A regular arrangement of the constituents particles ( atoms, molecules 
or ions ) in the three dimensional space which represent the geometry of 
a crystal is called space lattice.
There are only 14 possible three dimensional lattices. These are called 
Bravias lattices
Unit cell
The smallest repeating unit of the space lattice is called unit cell.
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FAQs on States of Matter - Gases, Liquids & Solids Class 11 Notes Chemistry

1. What are the different states of matter?
Ans. The different states of matter are gases, liquids, and solids. These states are determined by the arrangement and behavior of particles.
2. How are gases different from liquids and solids?
Ans. Gases are different from liquids and solids in terms of the arrangement and behavior of particles. Gas particles are far apart and move freely, while liquid particles are closer together and can flow, and solid particles are tightly packed and do not move freely.
3. What determines the state of matter of a substance?
Ans. The state of matter of a substance is determined by the intermolecular forces between its particles and the amount of thermal energy they possess. Strong intermolecular forces and low thermal energy result in a solid state, while weak intermolecular forces and high thermal energy result in a gas state.
4. How does temperature affect the state of matter?
Ans. Temperature affects the state of matter by influencing the amount of thermal energy in a substance. As temperature increases, the thermal energy of the particles also increases, causing them to move faster. This can lead to a change in state, such as a solid melting into a liquid or a liquid evaporating into a gas.
5. Can substances transition directly between all three states of matter?
Ans. Yes, substances can transition directly between all three states of matter. This is known as a phase change. For example, a solid can change directly into a gas through sublimation, and a gas can change directly into a solid through deposition. The conditions and specific substance determine whether these phase changes occur.
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