Thermodynamic Processes Overview

Overview

This lecture covers the definition of thermodynamic processes, describes various types (isothermal, adiabatic, isochoric, isobaric, cyclic), and explains reversible and irreversible processes.

Thermodynamic Process: Definition

• A thermodynamic process is a transformation of a system from one equilibrium state to another.
• During a thermodynamic process, properties such as temperature, pressure, and volume change.
• Energy can be transferred into or out of the system as heat or work.

Types of Thermodynamic Processes

Isothermal Process

• An isothermal process occurs at constant temperature (ΔT = 0).
• Example: Boiling water at a constant temperature.

Adiabatic Process

• An adiabatic process occurs without heat transfer between the system and surroundings (ΔQ = 0).
• System is perfectly insulated; energy is transferred only as work.
• Example: Hot water in an ideal thermos flask.

Isochoric Process

• An isochoric process has constant volume (ΔV = 0).
• No change in volume during the process.
• Example: Boiling water in a closed vessel.

Isobaric Process

• An isobaric process has constant pressure (ΔP = 0).
• No change in pressure during the process.
• Example: Boiling water in an open vessel.

Cyclic Process

• A cyclic process returns the system to its original state after a series of changes.
• There is no net change in internal energy (ΔE = 0) or enthalpy (ΔH = 0).
• Example: Carnot cycle in a heat engine.

Reversible and Irreversible Processes

Reversible Process

• The system and surroundings can return to initial states without any net change to the universe.
• Example: Melting and refreezing ice cream.

Irreversible Process

• The system and surroundings cannot be restored to original states after the process.
• Example: Mixing cement, sand, and water.

Key Terms & Definitions

• Thermodynamic Process — Change of a system from one equilibrium state to another.
• Isothermal Process — Process at constant temperature.
• Adiabatic Process — Process with no heat exchange.
• Isochoric Process — Process at constant volume.
• Isobaric Process — Process at constant pressure.
• Cyclic Process — Process that returns to original state.
• Reversible Process — Can be reversed with no net change to system or universe.
• Irreversible Process — Cannot be completely reversed.

Action Items / Next Steps

• Review each type of thermodynamic process and their real-life examples.
• Practice identifying each process in sample problems.