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1. PHYSICS PRESENTATION
Group-3
SUBMITTED BY
Md Mosharof Hosen-151002051
Mohammad Tareq Hosain-151002017
Mahmudul Hasan-151002030
S.N.I.Emon-151002022
Jannatul Nayem Nissan-151002064
Azajul Islam Rocky-151002073
SUBMITTED TO
Romena Akter
Faculty of EEE
Course Title: Physics Course Title: Phy 101
Sec- A
Depertment of Computer Science & Engineering

2. Thermodynamics laws,
Brownian motion,
Van der Waals equation of state,
Entropy.

3. POINTS OF DISCUSSION
 What is thermodynamics ?
 Thermodynamics laws.
 Definition of Brownian Motion.
 What is Brownian movement ?
 How are the brownian motion different from diffusion?
 Definition of Van der Waals equation of state.
 Van der Waals equation of state.
 Defination of Entropy
 Entropy of the System
 Entropy on the Molecular Scale
 Entropy Changes
 Any Questions ???

4. What is Thermodynamics ?
Thermodynamics:
Thermodynics is the field of
physics that deals with the relationship
between heat and other propertis ( such as:
pressure,density,temparature etc ) in a
substancs.

5. Thermodynamics laws :
The four laws of thermodynamics define fundamental
physical quantities that characterize thermodynamics
systems. The four laws of thermodynamics are:
Zeroth law of thermodynamics: If two systems are
in thermal equilibrium respectively with a third system, they
must be in thermal
equilibrium with
each other. This law
helps define the
notion of temperature.

6. Thermodynamics laws :
First law of thermodynamics: In all transformation
the amount of it supply to assistant must be balance by the
sum of the gain in internal energy of the system due to the
rise in temperature and the external work done.
Mathmatically,
dQ=dU+
where,
dQ=heat supplied
dU=change in internal energy
=heat equivaleat of the work done

7. Thermodynamics laws :
Second law of thermodynamics: In a natural
thermodynamic process, the sum of the entropies of the
participating thermodynamic systems, increases.
Equivalently,perpetual motion machines the second kind are
impossible.

8. Thermodynamics laws :
Third law of thermodynamics: The entropy of a
system approaches a constant value as the temperature
approaches absolute zero.With the exception of
glasses the entropy of a system at absolute zero is
typically close zero,and
is equal to the log of the
multiplicity of the
quantum ground state.

9. Definition of Brownian Motion
Brownian Motion: The brownian motion is the random
movemement of microscopic particles suspended in a
liquid or gas, caused by collisions with molecules of the
surrounding medium.
It was named for the Scottish botanist Robert Brown, the
first to study such fluctuations (1827).
This simple demonstration of
Einstein's explanation for Brownian
motion shows little particles batting
about a more massive one , and what

10. Brownian Motion:
it would look like if you could see only the massive one
through a microscope. Einstein showed that the overall
visible motion, averaged over many observations, exactly
matches what you would expect if the little particles were
atoms or molecules.

11. What is Brownian movement ?
Brownian movement: the random motion of small
colloidal particles suspended in a liquid or gas medium,
caused by the collision of the
medium's molecules with the
particles. Also called Brown′ian
movement.

12. How are the brownian motion different
from diffusion?
Brownian motion differs from diffusion most significantly in
that diffusion results in a net transfer of material from one
location to another on a macro scale, while Brownian motion
is randomly directed motion of molecules and similarly sized
particles and does not result in net mass transfer from one
place to another.

13. Definition of Van der Waals equation:
Van der Waals equation: The van der Waals
equation is an equation of state for a fluid composed of
particles that have a non-zero
volume and a pairwise attractive
inter-particle force (such as the
van der waals force).Not all gasses
act ideally. This is especially true
when one approaches the
conditions for the gas to condense.
Van der Waals’ state equation had
Van der Waals

14. Van der Waals equation:
become the most famous among those equations
that described the behavior of real gases. Afterwards,
Clausius, Virial, and others also proposed state
equations on real gases, but they were all based on
van der Waals’ equation.

15. Van der Waals equation of state:
 The ideal gas law, PV = nRT, can be derived by assuming
that the molecules that make up the gas have negligible
sizes, that their collision with themselves and the wall are
perfectly elastic, and that the molecules have no
interactions with each other.
 The van der Waal's equation is a second order
approximation of the equation of state of a gas that will
work even when the density of the gas is not low.

16. Van der Waals equation of state:
 Here a and b are constants particular to a given gas.
Some van der Waals Constants
Substance a
(J. m3/mole2)
b
(m3/mole)
Pc
(MPa)
Tc
(K)
Air .1358 3.64x10-5 3.77 133 K
Carbon Dioxide (CO2) .3643 4.27x10-5 7.39 304.2 K
Nitrogen (N2) .1361 3.85x10-5 3.39 126.2 K
Hydrogen (H2) .0247 2.65x10-5 1.30 33.2 K
Water (H2O) .5507 3.04x10-5 22.09 647.3 K
Ammonia (NH3) .4233 3.73x10-5 11.28 406 K
Helium (He) .00341 2.34x10-5 0.23 5.2 K
Freon (CCl2F2) 1.078 9.98x10-5 4.12 385 K

17. Van der Waals equation of state:
 The parameter b is related to the size of each molecule.
The volume that the molecules have to move around in is
not just the volume of the container V, but is reduced to ( V
- nb ).
 The parameter a is related to intermolecular attractive
force between the molecules, and n/V is the density of
molecules. The net effect of the intermolecular attractive
force is to reduce the pressure for a given volume and
temperature.
 When the density of the gas is low (i.e., when n/V is small
and nb is small compared to V) the van der Waals equation
reduces to that of the ideal gas law.

18. Van der Waals equation of state:
 One region where the van der Waals equation works
well is for temperatures that are slightly above the
critical temperature Tc of a substance

19. Van der Waals equation of state:
 Observe that inert gases like Helium have a low value
of a as one would expect since such gases do not
interact very strongly, and that large molecules like
Freon have large values of b.
 There are many more equations of state that are even
better approximation of real gases than the van der
Wall equation.

20. Defination of Entropy:
Entropy: In thermodynamics , entropy (usual
symbols) is a measure of the number of specific ways in
which a thermodynamics system be arranged, commonly
understood as a measure of disorder .
According to the second law of thermodynamics the
entropy of an isolated system maximum entropy. Systems
that are not isolated may decrease in entropy, provided
they increase the entropy of their environment by at least
that same amount. Since entropy is a state function, the
change in the entropy of a system is the same for any
process that goes from a given initial state to a given final
state, whether the process is reversible or irreversible.

21. Entropy of the System:
 Is greater in:
 Gases than solids.
 Larger volumes of gases than smaller volumes.
 Larger number of gas molecules than smaller number of
gas molecules.
 The change in entropy (ΔS) of a system was originally
defined for a thermodynamically reversible process as:

22. Example:
 Which has more entropy in its system?
H2O (s) or H2O (g)

23. Entropy on the Molecular Scale
 Ludwig Boltzmann described the concept of entropy on
the molecular level.
 Temperature is a measure of the average kinetic energy of
the molecules in a sample.

24. Entropy on the Molecular Scale
 Molecules exhibit several types of motion:
 Translational: Movement of the entire molecule from
one place to another.
 Vibrational: Periodic motion of atoms within a
molecule.
 Rotational: Rotation of the molecule on about an axis
or rotation about  bonds.

25. Entropy on the Molecular Scale
 Boltzmann envisioned the motions of a sample of
molecules at a particular instant in time.
 This would be akin to taking a snapshot of all the
molecules.
 He referred to this sampling as a microstate of the
thermodynamic system.

26. Entropy on the Molecular Scale
 Each thermodynamic state has a specific number of
microstates, W, associated with it.
 Entropy is
S = k lnW
where k is the Boltzmann constant, 1.38  1023 J/K.

27. Entropy on the Molecular Scale
 The number of microstates and, therefore, the
entropy tends to increase with increases in
 Temperature.
 Volume (gases).
 The number of independently moving molecules.

28. Entropy Changes
 In general, entropy increases when
 Gases are formed from liquids and solids.
 Liquids or solutions are
formed from solids.
 The number of gas
molecules increases.
 The number of moles
increases.

29. THANKS TO ALL