Laws of Thermodynamics

1. Laws of Thermodynamics

2. Review
Thermodynamics
 - can be defined as the science of energy.
In physics, thermodynamics is the study of energy
conversion between heat and mechanical work, and the
macroscopic variables such as temperature, volume and
pressure.
Energy- can be viewed as the ability to cause
changes.

3. First Law of Thermodynamics
The First Law states that energy cannot be created
nor destroyed; rather, the amount of energy lost in
a steady state process cannot be greater than the
amount of energy gained.

4. First Law of Thermodynamics
Example
Figure 1. Conservation of Energy for the Human Body

5. Second law of Thermodynamics
“Heat can spontaneously flow from a
higher-temperature region to a lower-
temperature region, but not the other
way around."
o Hot object will decrease in temperature and cold
object will increase in temperature until they are
both the same temperature.

7. Example
Figure 2. Heat flows in the direction of decreasing temperature.

8. Entropy:
Entropy is a measure of disorder.
Entropy is a measure of how evenly spread
out the energy is.
Entropy is a measure of energy that is no
longer “useful,” or “workable.”

9. Third law of Thermodynamics
The entropy of a system approaches a
constant value as the temperature
approaches absolute zero.
At zero temperature the system must be in a
state with the minimum thermal energy. This
statement holds true if the perfect crystal has
only one state with minimum energy.

10. Third law of Thermodynamics
Third Law states that the entropy of most pure
substances approaches zero as the absolute
temperature approaches zero.
 Entropy is related to the number of possible
microstates according to:
S = kB ln Ω
Where S is the entropy of the system, kB Boltzmann's
constant, and Ω the number of microstates

11. ZEROTH LAW
If two thermodynamic systems are in thermal
equilibrium with a third system, then they are in
thermal equilibrium with each other.
When two systems are put in contact with each
there will be a net exchange of energy between them
unless or until they are in thermal equilibrium. That is
the state of having equal temperature. Although this
concept of thermodynamics is fundamental.

12.  This law describes an
empirical parameter, the
temperature, as a property
of a system such that
systems in thermal
equilibrium with each other
have the same
temperature.
Zeroth law of thermodynamics

13. Thank You