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1. Properties Of Gases
TANDEL SUBHAM 150860131045
YASH S. JAIN 150860131012
YASH P. JAIN 150860131045
RAJ DAMANIA 150860131041
VIKSHIT GANJOO 150860131009
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2. Contents
 Boyle’s Law(constant temperature)
 Charles’ Law (constant pressure)
 Gay-Lussac Law(constant volume)
 Adiabatic Process
 Isothermal Process
 Polytropic Process

3. Boyle’s Law(Constant temperature)
• This law is named for Charles Boyle, who
studied the relationship between pressure, p,
and volume, V, in the mid-1600s.
• Boyle determined that for the same amount of
a gas at constant temperature, results in an
inverse relationship:
when one goes up, the other
comes down.
Robert Boyle
(1627-1691).
Son of Earl of
Cork, Ireland.

4. Boyle’s Law mean
Suppose you have a cylinder with a piston in the
top so you can change the volume. The cylinder
has a gauge to measure pressure, is contained so
the amount of gas is constant, and can be
maintained at a constant temperature.
A decrease in volume will result in increased
pressure.

5. Graphical Expressions of Boyle’s Law
Hyperbola
PV = constant
Straight Line
V = k / P
(y = mx + b)

6. Boyle’s Law at Work…
Doubling the pressure reduces the volume by half. Conversely, when the
volume doubles, the pressure decreases by half.

7.  Volume of a gas varies
directly with the absolute
temperature at constant
pressure.
 V = KT
 V1 / T1 = V2 / T2
Charles’ Law (Constant pressure)
Jacques-Alexandre Charles
Mathematician, Physicist, Inventor
Beaugency, France
November 12, 1746 – April 7, 1823

8. Charles’ Law mean
• This law is named for Jacques Charles, who
studied the relationship volume, V, and
temperature, T, around the turn of the 19th
century.
• This defines a direct relationship:
With the same amount of gas he found that
as the volume increases the temperature
also increases. If the temperature decreases
than the volume also decreases.

9. Charles’ Law: V1/T1 = V2/T2

10. Graphical Expressions of Charles’ Law
V = constant x T
Extrapolate to zero volume
same T regardless of P

11.  At constant volume, pressure and
absolute temperature are directly
related.
 P = k T
 P1 / T1 = P2 / T2
Gay-Lussac Law(Constant volume)
Joseph-Louis Gay-Lussac
Experimentalist
Limoges, France
December 6, 1778 – May 9, 1850
If n and V are constant,
then P α T
P and T are directly proportional.
P1 P2
=
T1 T2
If one temperature goes up, the pressure
goes up!

12. Gas Pressure, Temperature, and Kinetic
Molecular Theory
P proportional to T

13. Adiabatic Processes
l An adiabatic process is process in which there is no thermal
energy transfer to or from a system (Q = 0)
l A reversible adiabatic
process involves a
“worked” expansion in
which we can return all of
the energy transferred.
l In this case
PVg = const.
l All real processes are not.
p
V
2
1
3
4
T1
T2
T3T4

14. Basic Idea:
• No heat is added to or taken from the system
which we assume to be an air parcel
• Changes in temperature result from either
expansion or contraction
• Many atmospheric processes are “dry adiabatic”
• We shall see that dry adiabatic process play
a large role in deep convective processes
• Vertical motions
• Thermals
Parcel
0pdαdTcdq v 
0dpdTcdq p  

15. P-V Diagrams:
p
V
f
i
Isotherm
Isobar
Adiabat
Isochor

16. Isothermal process
• P,V may change but temperature is constant.
• The cylinder must have conducting walls
• It must happen very slowly so that heat produced during
compression is absorbed by surroundings and heat lost during
compression is supplied by surroundings.

17. Work done in isothermal process
• W=nRT ln(V2 /V1)
• So if V2 >V1 then W>0 that is work is
done by gas (isothermal expansion)
• and if V1 >V2 then W<0 that is work is
done on the gas (isothermal
compression).
p
V
3 T1
T2
T3T4

18. First law for isothermal process
• For an ideal gas,internal energy depends only on
temperature.Thus, there is no change in the internal
energy of an ideal gas in an isothermal process. The
First Law of Thermodynamics then implies that
• heat supplied to the gas equals the work done by the
gas : Q = W.

19. Polytropic Process (for Ideal Gas)
• The relationship between the pressure and volume during
compression or expansion of an ideal gas can be described
analytically. One form of this relationship is given by the
equation
pVn = constant
• where n is a constant for the particular process.
• A thermodynamic process described by the above equation is
called a Polytropic process.
• For a Polytropic process between two states 1-2
p V p Vn constant

20. Thank you