Its for Engineering students for thermodynamics

1. Prepared By......
Ronak Vaghasiya
As Student,
B.E. Mechanical 3rd Sem
Government Engg. Collage
Bhavnagar.

3. MATTER
Heterogeneous
mixture
Is it uniform
throughout?
No
Yes
Homogeneous
Can it be separated
by physical means?
No yes
Pure Substance Homogeneous
Mixture (solution)
Can it be decomposed
into other substance by
a chemical process?
No yes
Element Compound

4. Homogeneous Substances
• Means same throughout
1) element: only 1 type of atom
2) compound: 2 or more CHEMICALLY combined
elements (not easily separated from each other)
ex: water, CO2
3) Solution: a special kind of mixture 2 phases/parts
(SOLUTE dissolves & SOLVENT does the
dissolving)
ex: moist air (H2O in Air); sterling silver (Cu
in Ag…called an alloy)

5. Examples of Homogeneous mixture
Examples:
•Salt dissolved in water,
•Augar dissolved in water,
•Apple juice,
• Tea,
•Copper (II) sulfate solution in
water,
•Alloys....

6. INTRODUCTION ABOUT PURE
SUBSTANCE
A pure substance of constant chemical composition
throughout its mass.
It is a one-component system.
It may exist in one or more phases.
Here we take water as the representative of a pure
substance.

7. Phase of Pure Substance
The substances exist in different phases, e.g. At room
temerature and pressure ,copper is solid and mercury is
a liquid.
It can exist in different phases under variation of
condition
There is 3 principal phases
•solid
•Liquid
•Gas
Each with differnt molecular structures.

8. BASIC[1]
Triple Line/Point
• Area where all three phases can exist;
– Line on P-v and T-v diagrams
– Point on P-T diagrams

9. BASIC[2]
Sublimation • Two ways a substance can
go from solid to vapor:
– Melts to liquid, then
vaporizes to vapor
– Evaporates directly with
out first melting,
sublimation
• Happens at pressures
below triple point value

10. P-V DIAGRAM FOR PURE
SUBSTANCE[1]
Assume a unit mass of ice(solid water) at -10’c and 1 atm
contained in a cylinder and piston machine.(Fig. 1)
Let the ice be heated slowly so that its temperature is always
uniform.
Heating of H₂o at a
constant pressure of 1 atm.
Fig. 1

11. P-V DIAGRAM FOR PURE
SUBSTANCE[2]
Let the state changes of water be plotted on P-V coordinates
1-2 The temperature of ice increases from
-10˚C to 0˚C.
The volume of ice Would increase,as would
be the case for any solid upon heating.
At state 2 i.e., 0˚C,the ice would start melting.
2-3 Ice melts into water at a constnt
temperature of 0˚C.
At state 3,the melting process ends.
There is a decrease in volume,which is a
peculiarity of water.

12. P-V DIAGRAM FOR PURE SUBSTANCE[3]
3-4The temperature of water increases,upon
heating,from 0˚C to 100˚C.
The volume of water increases because of thermal
expantion.
4-5 The water start boiling at state 4 and boiling ends
at state 5.
This phase change from liquid to vapour occurs at a
constant temperature of 100˚C(the pressure being
constant at 1 atm).
There is a large increase in volume.

13. P-V DIAGRAM FOR PURE SUBSTANCE[4]
5-6 The vapour is heated
to,say 250˚C(state 6).
The volume of vapour
increases from v ₅to v₆.

14. P-V DIAGRAM FOR PURE
SUBSTANCE[5]
All the state changes of the system can similarly be
plotted on the p-v co-ordinates, when it is heated at
different constant pressures.
All the saturated solid state 2 at various pressures are
joined by a line(fig).

15. P-V-T SURFACE
The relationship between
pressure,specific volume,and temperature
can be clearly understood with the aid of a
three dimensional P-V-T surface.
There are two different surface for
different
substance of P-V-T surface.
1. Expand upon freezing[WATER]
2. Contract upon freezing[OTHER THAN WATER]

16. P-V-T SURFACE[Expanding]
Any point on p-v-T surface
represents an equilibrium state
of the substance.

17. P-V-T SURFACE[Contracting]
The triple point line when
projected to the p-T plane
becomes a point.
The critical isotherm has a
point of inflection at the critical
point.

18. Thank you