Khalid T MaaroofMSc. Pharmaceutical sciences

School of pharmacy – Pharmaceutics department

1Online access: bit.ly/physicalpharmacy

Thermodynamics

Physical Pharmacy

10/31/2015

outline:

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Thermodynamics??

Types of energyTerms and concepts

used in thermodynamics

Laws of thermodynamics.

Zero law

First law

Second law

Thied law

Thermodynamics

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

Forms of energy

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.

Definitions 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.

Thermodynamic systems

Thermodynamic systems

Energy Transfer: Heat and Work 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)Surrounding

s

HeatThe transfer of energy as a result of a temperature difference is called heat.

Work =(Force)x(distance) =Fd

Force=(Presssure)x(Area)

W=P(Ad)=PV

PV work is also called expansion work. There other types of work that are not discussed here.

Work

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• 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• This energy can be withdrawn as work or heat from the system.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

Zero law of thermodynamics

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

All heat is of th

e same kind !

First law of thermodynamicsThere Is No Free Lunch!!

Energy can not be created or destroyed only transformed

ΔEuniv=ΔEsys+ΔEsurr=0ΔEsys=−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

1st law of Thermodynamics is about Conservation of Energy 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.

Second law of thermodynamics 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.

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

(Qtr)=The quantity of heat transferred

Entropy 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.

Free energy 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.

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.

ΔG=ΔH−TΔSCase 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

Example: 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 spontaneous.

For more examples related to second law of thermodynamics refer to the appendix sheet file named ThermoEg(1) at:

bit.ly/physicalpharmacy

3rd Law of Thermodynamics

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.

Questions !

10/31/201525

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Quiz…!∆ H: +

∆ S: -Comment on spontaneity of a reaction at conditions above.

∆ G = ∆ H - T ∆ S

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