States of Matter & Gas Laws
States of Matter and Gas Laws - By Aditya
Abeysinghe
1

States of Matter
Matter can mainly be classified in three ways:
1. Classical States of matter
2. Non classical states of matter
3. States classified according to the energy
content in them.
Note: Although there exist different ways in
which matter can be classified, in this
presentation the prominence has been
given to the classical states of matter.
States of Matter and Gas Laws - By Aditya
Abeysinghe
2

On basis of energy
• Low temperature
states (E.g.: Super
fluids and Rydberg
molecules)
• High temperature
states (E.g.: Plasma
(ionized gases))
• Very high energy
states(E.g.:
Gravitational
Singularity)
Non Classical
states of matter
• Glass
• Liquid Crystals
Classical States of
matter
• Solid
• Liquid
• Gas
States of Matter and Gas Laws - By Aditya
Abeysinghe
3

Phase changes of matter
Solid Liquid
Gas
Plasma
Melting
Freezing
Deposition
Sublimation
Vaporization
Condensation
Deionization
Ionization
States of Matter and Gas Laws - By Aditya
Abeysinghe
4

Atmospheric Pressure
Atmospheric pressure is the force per unit area
exerted into a surface by the weight of air above
that surface.
Atmospheric pressure is calculated in various units. The following
equivalence is the most commonly used.
1 atm= 1×105 Pa= 760 mmHg= 760 torr
Atmospheric pressure can simply be measured by a barometer
by balancing the weight of mercury in the glass tube against the
atmospheric pressure.
States of Matter and Gas Laws - By Aditya
Abeysinghe
5

Temperature
It is a measure of the thermal energy of molecules
or atoms of a substance.
Temperature too has many units as pressure.
The relationship between these scales can be
summarized as follows:
F= (9/5) C +32 and K= C + 273
(Always K ≥ 0)
(Here F- Fahrenheit, C- Celsius, K- Kelvin)
States of Matter and Gas Laws - By Aditya
Abeysinghe
6

Gas Laws
There are six main gas laws associated with the
behavior of gases:
1. Boyle’s Law
2. Charles's Law
3. Combined Gas Law
4. Avogadro's law
5. Charles- Gay-Lussac’s law
6. Dalton’s law of partial pressure
States of Matter and Gas Laws - By Aditya
Abeysinghe
7

Boyle’s Law
Law: If the temperature is constant for a given
mass of a gas, the pressure varies inversely with
volume.
Applicable only if: Temperature stays constant
Applicable to:
1. Ideal gases at any temperature
2. Real gases which behave approximately as
ideal gases specially at high temperatures.
States of Matter and Gas Laws - By Aditya
Abeysinghe
8

Graphs of Boyle’s law
P
V
PV=k
P=k(1/V)
P
1/v
PV
P
PV= k
Log(PV)=Log k
Log P + Log V=Log k
Log P= Log k- Log V
Log P= -Log V+ Log k
Y = -mx + c
Log P
Log VStates of Matter and Gas Laws - By Aditya
Abeysinghe
9

Effect of external factors on a system
obeying Boyle’s Law
1. Effect of temperature 2. Effect of mass
Temperature increases
in the direction of the
arrow head keeping the
PV product constant
P
V
P
V
Mass increases
in the direction
of the arrow
head keeping
the PV product
constant
Temperature increases
Mass increasesPV PV
P P
States of Matter and Gas Laws - By Aditya Abeysinghe
10

Charles's Law
Law: If the pressure is kept constant for a given
mass of a gas the volume varies directly with the
absolute temperature.
Applicable only if: Pressure stays constant
Applicable to:
1. Ideal gases at any temperature
2. Real gases which behave approximately as
ideal gases specially at low pressures.
States of Matter and Gas Laws - By Aditya
Abeysinghe
11

Graphs of Charles’s Law
1. With absolute (K)
temperature
V
T(K)
2. With Celsius
temperature
‘Extrapolation’ shows that every gas
would achieve zero volume at -273.15 0C
-273.15 0C
V
T(0C)
States of Matter and Gas Laws - By Aditya
Abeysinghe 12

Effect of external factors on a
system obeying Charles’s Law
1. Effect of pressure 2. Effect of mass
V
T(K)
V
T(K)
Pressure increases in
the direction of the
arrow head
Mass increases in the
direction of the arrow
head
States of Matter and Gas Laws - By Aditya
Abeysinghe
13

Combined Gas Law
PV
T
k
When P is maintained constant,
V/T = k. Therefore the system obeys
the Charles’s law.
When T is maintained
constant, PV = k.
Therefore the system
obeys the Boyle’s law.
States of Matter and Gas Laws - By Aditya
Abeysinghe
14

Avogadro’s law
Law: Equal volumes of gases at the same
temperature and same pressure contain the
same no. of molecules/atoms.
Modified law: Equal volumes of gases at the
same temperature and same pressure contain
the same no. of moles.(Since no. of moles=
no. of atoms or molecules × Avogadro Number)
States of Matter and Gas Laws - By Aditya
Abeysinghe
15

Charles-Gay Lussac Law
The second form of the Charles's law describes
that there exist a direct relationship between
the pressure and the absolute temperature of
a system if the volume is kept constant.
Then, P/T = k.
This can also be obtained from the combined
gas law by keeping V constant.
States of Matter and Gas Laws - By Aditya
Abeysinghe
16

Dalton’s Law of Partial Pressures
Law: The pressure of a mixture of gases is the
sum of the partial pressures of its parts.
Therefore, a gas mixture which holds O2 and N2
has a total pressure of :
Ptotal = Poxygen + Phydrogen
In a similar way the unsaturated gas pressure of
a gas containing vapor can be calculated.
States of Matter and Gas Laws - By Aditya
Abeysinghe
17

General/Ideal gas equation
PV= nRT
(R- Universal Gas Constant)
i. When mass and temperature are constant, n and T become
constant. Since R is also a constant for any gas, PV = k. Thus, when
the mass and the temperature are constant, from the above
equation, the system obeys Boyle’s Law.
ii. When mass and pressure are constant, P ,R and T are constant. Thus
V/T = k or the system, from the above equation, obeys Charles’s Law.
iii. When mass and volume are constant, V, n and R are constant.
Thus, from the above equation, P/T is a constant. P/T = k.
Therefore, the system obeys Charles- Gay Lussac (Charles’s 2nd ) Law.
iv. When P, V and T are constant, The no. of moles, molecules or atoms
for a particular gas is a constant. Thus, the no. of moles, molecules
or atoms of one gas is equal to that of another gas at the same
temperature, same volume and under same pressure. Thus the
system obeys Avogadro’s Law.
States of Matter and Gas Laws - By Aditya
Abeysinghe
18

About the Universal Gas Constant
Universal gas constant is a value/expression that is
independent of the used gas and other physical
factors (such as Pressure, Temperature, Volume…).
Its value is 8.314J/(mol.K)
It also displays a relationship with the Boltzmann
Constant as ,
Boltzmann Constant = Universal Gas Constant/
No. of molecules or atoms in the gas
States of Matter and Gas Laws –
By Aditya Abeysinghe
19

Summarizing it up!!!!
Ideal gas
equation
PV =nRT
Gas law
problems
Combined gas
equation
(PV)/T = k
Charles-Gay
lussac’s law
P/T = k
Charles’s law
V/T = k
Boyle’s law
PV= k
When
either
mass or
the no.
of moles
are given
When the
mass of a
given gas is
constant
When T1 = T2 When P1= P2
When V1= V2
States of Matter and Gas Laws - By Aditya
Abeysinghe
20