Thermodynamics(Physical Pharmacy)

1. Khalid T Maaroof
MSc. Pharmaceutical sciences
School of pharmacy – Pharmaceutics department
1
Online access: bit.ly/physicalpharmacy
Thermodynamics
Physical Pharmacy
10/31/2015

2. outline:
2
Thermodynamics??
Types of energy
Terms and concepts used
in thermodynamics
Laws of thermodynamics.
Zero law
First law
Second law
Thied law

3. Thermodynamics
3
 Thermodynamics is about energy, its flow and its
transformation from one form into another form.

4. Forms of energy
4
The INTERNAL ENERGY, E of a system is the sum of the kinetic and
potential energies of all the particles that compose the system or the total
energy of a system.

5. Definitions
5
 System: A region of the universe that we direct our
attention to.
 Surroundings: Everything outside a system is
called surroundings.
 Boundary: The
boundary or wall
separates a system
from its surroundings.

6. 6

7. Thermodynamic systems
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8. 8
Thermodynamic systems

9. Energy Transfer: Heat and
Work
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 Both work and heat together allow systems to exchange
energy
 Heat is the transfer of thermal energy between two bodies that
are at different temperatures
 Work is the force used to transfer energy between a system
and its surroundings, and is needed to create heat and the
transfer of thermal energy.
System
Heat (q)
Work (w)
Surroundings

10. Heat
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The transfer of energy as a result of a temperature difference is called heat.

11.  Work =(Force)x(distance)
=Fd
 Force=(Presssure)x(Area)
 W=P(Ad)
=PV
 PV work is also called expansion
work. There other types of work
that are not discussed here.
Work

12. 12
• Energy may enter the system as heat or work.
• The energy is stored as potential energy (PE) and kinetic energy
(KE).
• This energy can be withdrawn as work or heat from the system.
Energy Transfer: Heat and
Work

13. Zero law of thermodynamics
13
 The Zero Law of Thermodynamics states that if two
systems are in thermodynamic equilibrium with a
third system, the two original systems are in thermal
equilibrium with each other.
System A
System C
System B

14. First law of thermodynamics
There Is No Free Lunch!!
14
 Energy can not be created or destroyed only
transformed
ΔEuniv=ΔEsys+ΔEsurr=0
ΔEsys=−ΔEsurr
 The First Law of Thermodynamics states that energy
can be converted from one form to another with the
interaction of heat, work and internal energy, but it
cannot be created nor destroyed, under any
circumstances.
 ΔE=Q+W

15. 1st law of Thermodynamics is about
Conservation of Energy
15
 As heat is applied to a closed system, the system
does work by increasing its volume.
 w=PΔV
The sum of heat and work is the change in internal energy, ΔE.
In an isolated system, Q=−W. Therefore, ΔE=0.

16. Second law of thermodynamics
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 Second law of thermodynamics is about spontaneity
of processes.
 Heat does not go from a colder body to a hotter
body.
 flow of heat is always from a hotter body to a colder
body.
 The entropy of the universe will increase during any
spontaneous change.

17.  Entropy is the measure of disorder
 Qtr ∝ T
 ΔS ∝ Qtr
 Entropy increases with softer, less rigid solids, solids
that contain larger atoms, and solids with complex
molecular structures.
Entropy
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(Qtr)=The quantity of heat transferred

18. Entropy
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 The Second Law of Thermodynamics states that the
state of entropy of the entire universe, as a closed
isolated system, will always increase over time. The
second law also states that the changes in the
entropy in the universe can never be negative.

19. Free energy
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 ΔG=ΔH−TΔS
 ΔH refers to the heat change for a reaction. A positive ΔH means that heat
is taken from the environment (endothermic). A negative ΔH means that
heat is emitted or given to the environment (exothermic).
 ΔG is a measure for the change of a system's free energy.

20. 20
 If ΔG < 0, the process occurs spontaneously.
 If ΔG = 0, the system is at equilibrium.
 If ΔG > 0, the process is not spontaneous as written
but occurs spontaneously in the reverse direction.

21. ΔG=ΔH−TΔS
21
Case ΔH ΔS ΔG Reaction
1. high temperature - + - Spontaneous
2. low temperature - + - Spontaneous
3. high temperature - - + Nonspontaneous
4. low temperature - - - Spontaneous
5. high temperature + + - Spontaneous
6. low temperature + + + Nonspontaneous
7. high temperature + - + Nonspontaneous
8. low temperature + - + Nonspontaneous

22. Example:
22
O2 2 O
occurs spontaneously under what temperature
conditions?
 Answer:
 By simply viewing the reaction one can determine that the
reaction increases in the number of moles, so the entropy
increases.
 The enthalpy is positive, because covalent bonds are
broken. When covalent bonds are broken energy is
absorbed, which means that the enthalpy of the reaction is
positive. So, if the temperature is low it is probable
that ΔH is more than T∗ΔS, which means the reaction is not
spontaneous. If the temperature is large then T∗ΔS will be
larger than the enthalpy, which means the reaction is

23. 23
 For more examples related to second law of
thermodynamics refer to the appendix sheet file named
ThermoEg(1) at:
bit.ly/physicalpharmacy

24. 3rd Law of Thermodynamics
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 It says that however it is impossible to reach absolute
zero, but at which (0 Kelvin), there will be no entropy
(S) and a pure crystalline structure of matter will form.

25. Questions !
10/31/201525

26. Quiz…!
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∆ H: +
∆ S: -
Comment on spontaneity of a
reaction at conditions above.
∆ G = ∆ H - T ∆ S

27. Video files
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 https://www.youtube.com/watch?v=jNPUCmkKiE4
1st law experiment
 https://www.youtube.com/watch?v=7OJG-ZHrbD8
 2nd law experiment