A pure substance has a homogeneous and invariable chemical composition and may exist in more than one phase, such as water existing in solid, liquid, and vapor phases. At temperatures and pressures above the critical point, the discrete phase transition from liquid to vapor is no longer present. Phase diagrams can be used to represent the different phases of pure substances at various temperatures and pressures.

1. Properties of Pure Substances
S.Gunabalan
Associate Professor
Mechanical Engineering Department
Bharathiyar College of Engineering & Technology
Karaikal - 609 609.
e-Mail : gunabalans@yahoo.com
Part - 2

2. Properties of Pure Substances
• Pure Substance
A pure substance has a homogeneous and
invariable chemical composition and may exist in
more than one phase.
Examples:
1. Water (solid, liquid, and vapor phases)
2. Mixture of liquid water and water vapor
3. Carbon dioxide, CO2
4. Nitrogen, N2

3. Properties of Pure Substances

4. Properties of Pure Substances

5. Properties of Pure Substances
At temperatures and pressures above the critical point, the phase transition
from liquid to vapor is no longer discrete.

6. Properties of Pure Substances

7. Properties of Pure Substances

8. Properties of Pure Substances

9. Phase diagram of pure substances

10. Reference
• Rajput, R. K. 2010. Engineering thermodynamics. Jones and Bartlett
Publishers, Sudbury, Mass.
• Nag, P. K. 2002. Basic and applied thermodynamics. Tata McGraw-Hill, New
Delhi.
• http://www.wiley.com/college/moran/CL_0471465704_S/user/tutorials/t
utorial2/state_princ/pv_dome.jpg