Thermodynamics
Thermodynamics
Definition
Thermodynamics is the branch of physics that deals with heat, work, temperature, and the laws governing the transfer of energy.
Key Concepts
System and Surroundings
System: The part of the universe being studied (e.g., a gas in a container).
Surroundings: Everything outside the system.
Types of Systems
Open System: Can exchange both energy and matter with surroundings.
Closed System: Can exchange energy but not matter.
Isolated System: Cannot exchange energy or matter.
State Functions
Properties that depend only on the state of the system, not on how it got there (e.g., temperature, pressure, volume, internal energy).
Processes
Isothermal: Constant temperature.
Adiabatic: No heat exchange.
Isobaric: Constant pressure.
Isochoric: Constant volume.
Laws of Thermodynamics
Zeroth Law
If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
First Law (Law of Energy Conservation)
Energy cannot be created or destroyed, only transformed.
Formula: ΔU = Q - W
ΔU = Change in internal energy
Q = Heat added to the system
W = Work done by the system
Second Law
The total entropy of an isolated system can never decrease over time.
Heat cannot spontaneously flow from a colder body to a hotter body.
Third Law
As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Key Terms
Heat (Q): Energy transferred due to temperature difference.
Work (W): Energy transfer that results from a force acting over a distance.
Internal Energy (U): Total energy contained within a system.
Entropy (S): Measure of disorder or randomness in a system.
Applications
Heat Engines: Convert heat energy into work (e.g., car engines).
Refrigerators: Transfer heat from a cooler to a warmer area.
Thermal Efficiency: Ratio of useful work output to heat input.
Important Equations
Ideal Gas Law: PV = nRT
P = Pressure, V = Volume, n = number