Thermodynamics

Thermodynamics

The branch of physics that deals with heat, work, temperature, and the laws governing the transfer of energy.

System

The part of the universe being studied (e.g., a gas in a container).

Surroundings

Everything outside the system.

Open System

A system that can exchange both energy and matter with its surroundings.

Closed System

A system that can exchange energy but not matter.

Isolated System

A system that 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).

Isothermal Process

A process that occurs at constant temperature.

delta

Adiabatic Process

A process in which there is no heat exchange.

Isobaric Process

A process that occurs at constant pressure.

Isochoric Process

A process that occurs at constant volume.

Zeroth Law of Thermodynamics

If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed; expressed as ΔU = Q - W.

ΔU

Change in internal energy of a system.

Q = mcΔT

Heat Added to the System

1. 
   

   
   

   First Law of Thermodynamics:[ \Delta U = Q - W ]Where:

   • ( \Delta U ) = Change in internal energy

   • ( Q ) = Heat added to the system

   • ( W ) = Work done by the system

2. 
   

   
   

   Heat Transfer:[ Q = mc\Delta T ]Where:

   • ( m ) = Mass of the substance

   • ( c ) = Specific heat capacity

   • ( \Delta T ) = Change in temperature

3. 
   

   
   

   Phase Change:[ Q = mL ]Where:

   • ( L ) = Latent heat (fusion or vaporization)

These formulas are fundamental in thermodynamics for calculating heat transfer in various processes.

Heat added to the system.

W = F · d · cos(θ)

W

Work done by the system.

Second Law of Thermodynamics

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 of Thermodynamics

As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Heat (Q)

Energy transferred due to a temperature difference.

Work (W)

Energy transfer that results from a force acting over a distance.

W = -P gas delta=V=-nRdeltaT=-deltangRT

Internal Energy (U)

Total energy contained within a system.

Entropy (S)

Measure of disorder or randomness in a system.

state function. and extensive property. For cyclic process. Delta S cyclic = 0.

Isothermal Process:

• Formula: The change in entropy (ΔS) can be calculated using the formula:

• ΔS = nRln(Vf/Vi),

• General Formula:

  • Formula: ΔS=QT\Delta S = \frac{Q}{T}ΔS=TQ​

Thermal Efficiency

The ratio of useful work output to heat input.

Ideal Gas Law

An equation of state for an ideal gas, expressed as PV = nRT.