2. THERMODYNAMICS
literally means “moving or
evolving heat.” The science of
thermodynamics is concerned
with heat and its transformation
to mechanical energy.

3. SYSTEM - object or collection of objects
under study. Everything else is referred
to as surroundings
The system and the surroundings
constitute the universe.
INTERNAL ENERGY- refers to the sum of
the kinetics energies of the molecules
of a body and the potential energy to
intermolecular forces

4. REVERSIBLE PROCESS –
one in which the system and its
surroundings can be returned to their
initial state before the process occurs

5. IRREVERSIBLE PROCESS - one in which
the system and its surroundings
cannot be returned to their initial state
before the process occurs. Also
known as the natural process.

7. ZEROTH LAW OF THERMODYNAMICS
A
B C
“If object A is in thermal equilibrium with
object B and object A is in thermal equilibrium
with a third object C, then object B must be in
equilibrium with object C”

8. Thermal Equilibrium- the main concern of
the zeroth law, two bodies are said to be in
thermal equilibrium if they have the same
temperature.

9. THE FIRST LAW OF THERMODYNAMICS
“When heat is added to a system, some of it
remains in the system increasing its internal
energy, while the rest leaves the system as the
system does work.”

10. THE SECOND LAW OF THERMODYNAMICS
 Three versions of the second law of thermodynamics:
 KELVIN-PLANCK STATEMENT – no heat
engine can completely convert heat energy to
work . In other words, there is no 100% efficient
heat engine.
 CLAUSIUS STATEMENT – heat flows
naturally from hot to cold objects .
 ENTROPY STATEMENT – when a reversible
process occurs, the total entropy of the universe
remains the same. When an irreversible process
occurs, the total entropy of the universe
increases.

11. Entropy is an abstract or theoretical quantity. It
is used to predict the direction of natural
events and to predict whether a given
chemical or physical process is possible. If
the process is found to be impossible,
additional data may tell scientist what can be
done to make the process possible.

12. THE THIRD LAW OF THERMODYNAMICS
“The entropy of a perfect crystal of a substance at
the absolute zero temperature is zero.”

14. HEAT ENGINES
a device that converts heat
energy to mechanical work

15. TYPES OF HEAT ENGINES
 INTERNAL COMBUSTION
ENGINE – burns the fuel inside
the engine.
 EXTERNAL COMBUSTION
ENGINE - burns the fuel
outside the engine.

16. STEAM ENGINES
HERO OF ALEXANDRIA
– invented the oldest heat
engine since 200 B. C.
called Aeolipile in which
steam was conducted
through pipes from a
boiler.

17. Aeolipile

18. THOMAS SAVERY –
developed the first
commercial steam
engine in 1968.

19. Savery Engine

20. THOMAS
NEWCOMEN – came
up with a modified
engine using steam at
atmospheric pressure
in 1712.

21. Newcomen Engine

22. JAMES WATT –
introduced a greatly
improved steam engine
with a separate
condenser in 1769. This
invention triggered the
so called “Industrial
Revolution” and
stimulated the
inventions of other
types of engine.

23. Watt Steam Engine

24. GASOLINE AND DIESEL ENGINES
The gasoline engine and diesel
engine are internal combustion
engines. These engines operate on
four different stokes: intake,
compression, power and exhaust.

26. IDEAL HEAT ENGINE
Maximum efficiency is obtained if all
processes undergone by the working
substance of a heat engine are reversible.
This statement is called Carnot principle,
named after French engineer Sadi Carnot.
The Carnot engine is a hypothetical heat
engine undergoing all reversible process.

27. WHAT YOU SHOULD KNOW:
• You should know that efficiency is a comparison of the useful
work energy provided by a machine or system to the work
energy applied to the machine or system.
• You should know that the formula for efficiency is:
input work
efficiency= x 100%
output work
• You should know that the parts of a machine or system and how
they are connected together will affect the machine's or
system's efficiency.
• You should know that other forces such as friction will affect an
object's movement.
• You should know that velocity ratio is a comparison of
the distance a load moves to the distance travelled by the force
needed to move it.