Introduction to Thermodynamics

Thermodynamics Definition

• Thermodynamics is a branch of physics that analyzes heat, work, temperature, and their relation to energy, radiation, and physical properties of matter.
• It focuses on how thermal energy is converted to or from other forms of energy and how this process affects matter.

Thermal Energy

• Thermal energy is the energy associated with heat.
• This heat is generated by the movement of tiny particles within an object.
• The faster these particles move, the more heat is generated.

Distinction Between Mechanics and Thermodynamics

• Mechanics focuses solely on the motion of particles or bodies under forces and torques.
• Thermodynamics focuses on the internal macroscopic state of a system, not its overall motion.

Branches of Thermodynamics

• Classical Thermodynamics analyzes matter behavior with a macroscopic approach, considering units like temperature and pressure to predict characteristics.
• Statistical Thermodynamics analyzes the properties of individual molecules and their interactions to understand the behavior of a group of molecules.
• Chemical Thermodynamics studies the relationship between work and heat in chemical reactions and state changes.
• Equilibrium Thermodynamics studies energy and matter transformations as they approach equilibrium.

Thermodynamic Systems

• A system is a specific portion of matter with a definite boundary that is the focus of study.
• The boundary can be real or imaginary, fixed or deformable.
• Isolated Systems cannot exchange energy or mass with their surroundings.
• Closed Systems can exchange energy but not mass with their surroundings.
• Open Systems can exchange both energy and mass with their surroundings.

Surrounding

• The surrounding is everything outside the system that directly influences its behavior.

Thermodynamic Processes

• A thermodynamic process is a change in a system's energy state that is associated with changes in pressure, volume, and internal energy.
• Adiabatic Process involves no heat transfer into or out of the system.
• Isochoric Process involves no change in volume and no work done by the system.
• Isobaric Process involves no change in pressure.
• Isothermal Process involves no change in temperature.

Isothermal Process

• The temperature remains constant throughout this process.
• If work is done on the system, the internal energy is reduced by the amount of work done.
• If work is done by the system, the internal energy is increased by the amount of work done.

Adiabatic Process

• No heat is exchanged between the system and the surrounding.
• Work done on the system increases the internal energy.
• Work done by the system decreases the internal energy.

Isochoric Process

• The volume remains constant.
• No work is done by the system.

Isobaric Process

• The pressure remains constant.
• Work done is related to the change in volume.
• Increase in volume = positive work done.
• Decrease in volume = negative work done.

Enthalpy

• Enthalpy is the measurement of total heat content in a system, considering its internal energy, volume, and pressure.
• H = E + PV

Entropy

• Entropy is a thermodynamic quantity that measures the randomness or disorder of a system.
• Higher entropy indicates a greater degree of randomness or disorder.

Thermodynamics Laws

• Zeroth Law of Thermodynamics: If two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
• First Law of Thermodynamics: Energy cannot be created or destroyed, only transferred from one form to another.
• Second Law of Thermodynamics: The entropy of an isolated system always increases.
• Third Law of Thermodynamics: The entropy of a system approaches a constant value as the temperature approaches absolute zero.

Importance of Laws of Thermodynamics

• These laws define fundamental physical quantities (temperature, energy, entropy), which characterize thermodynamic systems at thermal equilibrium.

Energy Conservation

• Energy cannot be destroyed or lost, only transformed from one form to another.

First Law of Thermodynamics in Action

• Everyday examples like sweating in a crowded room illustrate the applications of the first and second laws of thermodynamics.