This document provides a brief introduction to phase transitions, including: 1) It defines a phase as a region of uniform physical properties and discusses the main states of matter. 2) It explains that a phase transition occurs when a system transforms between phases via heat transfer, changing its thermodynamic parameters and often its symmetry. 3) It outlines the main types of phase transitions - first order, second order, and lambda - based on properties like latent heat and discontinuities in heat capacity or thermodynamic free energy derivatives.

1. BY:
PREMASHIS KUMAR
SUDIPTA KUMAR DASH
PHASE TRANSITION:
A BRIEF INTRODUCTION
SUBMITTED TO:
DR.AJIT KUMAR PATRA

2. INTRODUCTION
WHAT IS PHASE TRANSISION
TYPES OF PHASE TRANSITION
FIRST ORDER PHASE TRANSITION
SECOND ORDER PHASE
TRANSITION
CONCLUSION
CONTENTS

3. INTRODUCTION
A phase is a region of space (a thermodynamic system), throughout which
all physical properties of a material are essentially uniform.
phase is used as a synonym for state of
matter.
 Plasma - the "fourth phase“.
A single material may have several
distinct solid states capable of forming separate phases.

4. • The state of a system can be described in terms of its degrees of freedom.
• Macroscopic quantity of gas Order of 1023 particles Having many
degrees of freedom number of thermodynamic degrees of freedom is
few.
• A phase transition is the transformation of a thermodynamic system from
one phase or state of matter to another one by heat transfer.
• A phase transition is achieved by
changing the thermodynamic parameters.
• In a large class of phase transitions , the
system undergoes a symmetry change.

5. TYPES OF PHASE TRANSITION
PHASE
TRANSITION
Mechanistic
classification
(Buerger,1951)
Order-
disorder
Displacive Reconstructive
Thermodynamic
classification
Modern
classification
Based on
Latent
Heat
FIRST ORDER
TRANSITION
SECOND
ORDER
TRANSITION
Ehrenfest
classification
(1933)
Based on
thermodynamic
free energy
FIRST ORDER
TRANSITION
SECOND
ORDER
TRANSITION

6. ORDER OF TRANSITION
• The order of the transformation = the lowest derivative (n) of
Gibbs free energy which shows a discontinuity at the transition
point.
• n=1 First order
• n=2 Second order.
1
1
(thermodynamic Variable)
(External Variable)
n
n


 
 
 
1
1
(G)
0
(T)
C
n
n
T T



 
  
 
(G)
0
(T)
n
n
P
 
  
 

7. FIRST ORDER PHASE TRANSITION
The first-order phase transitions are those that involve a latent heat.
A first order phase transformation should satisfy the following two requirements:
1. There are changes in entropy and volume .
2. The first order derivatives of Gibbs function change discontinuously.
• The first order phase transition occurs between the triple point and critical point.
For a reversible isothermal isobaric phase Transition,
dg=0 i.e. 𝑮𝒊 = 𝑮 𝒇 .
dG=-SdT+VdP
 first-order transitions are associated with "mixed-
phase regimes“.

8. At the transition point, we
are changing the enthalpy of
the system but not its
temperature . The heat
capacity Cp at the transition
point is infinite.

9. The Clausius-Clapeyron equation
Clausius-Clapeyron equation pertains to the relationship between
the pressure and temperature for conditions of equilibrium
between two phases.
dP/dT = L/(T(Vf-Vi))
L is the specific latent heat.
• Clausius- Clapeyron’s equation can
be used to estimate the latent heat
if ,P,V and T are known.

10. SECOND ORDER PHASE TRANSITION
• For second order phase transition:
1. There are no changes of entropy and specific volume.
2. Molar Gibbs function is continuous.
3. First order derivative of G is continuous.
4. Second order derivatives of G changes discontinuously.
• The second order phase transition occurs at the critical point and At critical
point the latent heat of vaporization, L is zero.
• EXAMPLE:
1. Transition of a super conductor from super conducting to the normal state in
zero magnetic field.
2. Ferromagnetic to paramagnetic transition in a simple model.

11. S and V do not
jump at transition)
Finite discontinuity in CP (NOT infinite).

12. LAMDA TRANSITIONS
• Third type of phase transition between the two liquid phases of ordinary
𝑯𝒆 𝟒liquid helium l and super fluid helium ll.
• This transition can occur at any point along the line separating these two
liquid phases.
The value of Heat capacity does
not change discontinuously, but its variation with temperature is different in the two
phases.

13. THANK YOU