fUNDAMENTALS

system

is defined as a quantity of matter or a region in space chosen for study.  

surroundings

he mass or region outside the system is called the .

Boundary

: the real or imaginary surface that separates the system from its surroundings.

Thermodynamics

is the science of energy and its transformations.

• Heat and work interactions

• Energy conversion processes

• Properties of matter

• Equilibrium states

thermo It studies:

therme (heat) + dynamis (power)

thermodynamics The word comes from Greek:

• Power Generation

HVAC & Refrigeration

• Chemical Processes

• Aerospace

Why Study Thermodynamics?

• Automotive Engines

• Power Plants

• Refrigerators & AC

• Jet Engines

• Weather Systems

• Biological Systems

Real-World Applications

 CLOSED SYSTEM (CONTROL MASS)

➳ No mass can cross system boundary

➳ Energy may cross system boundary

➳ Volume is NOT fixed

OPEN SYSTEM/CONTROL VOLUME

➳ Mass may cross system boundary (Control surface)

➳ Volume may/may not be fixed

➳ Energy may cross system boundary

➳ Control Volumes may operate at steady state, or change with time (empty/fill)

 

1. MACROSCOPIC VIEW (CLASSICAL THERMODYNAMICS)

➳ Focuses on the overall behavior of a system (like pressure, temperature, volume).

➳ Does not look at molecules or atoms individually.

➳ Uses observable properties to describe and predict system behavior.

 Example: Measuring the pressure and temperature of steam in a boiler without analyzing each water molecule.

2. MICROSCOPIC VIEW BEHAVIOR.]

➳ Looks at the molecular, atomic, or subatomic level.

➳ Explains how the structure and motion of particles affect system

Example: Using statistical mechanics to understand how billions of molecules create pressure in a gas.

 

3. PROPERTY

is a measurable characteristic of a system.

Examples: mass, volume, pressure, temperature, energy.

4. STATE

➳ The condition of a system described by its properties.

Example: If you know the pressure and temperature of steam, you can determine its density and energy content.

PROCESS

➳ A change from one state to another.

➳ If properties don't change with time > the system is at steady state

Example: Heating water from room temperature to boiling point.

6. CYCLE

➳ series of processes that returns the system to its original state.

all properties are the same as at the beginning.

Example: Steam in a power plant goes through heating, expansion, cooling, and compression, then ends up back where it started.

PHASE

is a portion of matter that is uniform in both chemical composition and physical structure.

➳ Uniform physical structure: All solid, all liquid, or all gas/vapor.

8. PURE SUBSTANCE

has a uniform and unchanging chemical composition.

➳ Can exist in multiple phases: As long as the chemical composition is the same in each phase.

 

EXTENSIVE PROPERTIES

➳ A property is called _____ if its value for an overall system is the sum of its values for the parts into which the system is divided.

Examples: Mass, volume, energy.

Key Point: If you divide the system into smaller pieces, the property values add up to the whole.

2. INTENSIVE PROPERTIES

 ➳ Do not depend on the size or amount of the system. The value stays the same no matter how the system is divided.

Examples: Temperature, pressure, density, specific volume.

LAW OF CONSERVATION OF MASS

➳ Mass can neither be created nor destroyed in an ordinary physical or chemical process.

➳ The total mass entering a system equals the total mass leaving plus any mass stored within

➳ Applies to all systems: open, closed, and isolated

➳ Foundation for mass balance equations in engineering

STEADY-STATE MASS BALANCE

➳ properties do not change with time.

➳ This simplifies the mass balance:

        

PRESSURE

is a scalar quantity — it acts equally in all directions at a point in a fluid (Pascal's Law).

ABSOLUTE PRESSURE

➳ Measured relative to perfect vacuum.

GAUGE PRESSURE

➳ Measured relative to atmospheric pressure.

VACUUM PRESSURE

➳ When absolute is below atmospheric.

BAROMETER

➳ Measures atmospheric pressure using mercury column height. Use: Weather stations

MANOMETER

2. ➳ U-tube with fluid to measure pressure differences. Use: Lab experiments

BOURDON GAUGE

3. ➳ Curved tube that straightens under pressure. Use: Industrial applications

TRANSDUCER

4. ➳ Converts pressure to electrical signal. Use: Digital systems

HYDROSTATIC PRESSURE

➳ Pressure increases linearly with depth in an incompressible fluid.

TEMPERATURE

➳ is a measure of the average kinetic energy of molecules in a substance.

➳ Thermal equilibrium:

no net heat transfer between objects at the same temperature

ZEROTH LAW OF THERMODYNAMICS

➳ If two bodies are each in thermal equilibrium with a third body, they are in thermal equilibrium with each other.