Introduction to Thermodynamics

Introduction to Thermodynamics

• Thermodynamics is the science of energy and its transformation, and its effects on physical properties of substances.
• It deals with equilibrium and feasibility of a process, and the relationship between heat and work, and the properties of systems in equilibrium.

Thermodynamics System

• A thermodynamics system is defined as a quantity of matter or a region in space chosen for study.
• The mass and region outside the system is called the surrounding.
• The boundary of the system is a real or imaginary surface that separates the system from the surrounding.

Types of Thermodynamics Systems

• Closed System (Control Mass): A fixed amount of mass, no mass can cross its boundary, and energy can cross the boundary in the form of heat or work.
• Open System (Control Volume): A properly selected region in space where both mass and energy can cross the boundary.

Approaches to Thermodynamics

• Macroscopic Approach: Considers a certain quantity of matter without taking into account events occurring at the molecular level.
• Microscopic Approach: Considers the matter as comprised of a large number of tiny particles known as molecules, which move randomly in a disordered fashion.

Properties of a System

• Property: Any characteristic of a system.
• Intensive Properties: Independent of the size of the system, such as temperature, pressure, and density.
• Extensive Properties: Depend on the size or extent of the system, such as mass, volume, and total energy.

Specific Properties of a System

• Specific Properties: Extensive properties per unit mass.
• Specific Volume: The volume of a substance per unit mass.
• Specific Energy: The energy of a substance per unit mass.
• Specific Gravity: The density of a substance with respect to the density of a standard substance at a specified temperature.

Continuum and State

• Continuum: A continuous, homogeneous matter with no holes.
• State: The condition of a system at any instant of time, described by its properties.

Equilibrium and Processes

• Equilibrium: A state of balance, with no unbalanced potentials or driving forces within the system.
• Process: A change that a system undergoes from one equilibrium state to another.
• Quasi-Equilibrium Process: A process that proceeds in a manner that the system remains infinitesimally close to an equilibrium state at all times.

Point Function and Path Function

• Point Function: A quantity whose change is independent of the path, such as properties.
• Path Function: A quantity whose value depends on the path followed during a change of state, such as heat and work.

Cycle and Steady Flow Process

• Cycle: A system that returns to its initial state at the end of a process.
• Steady Flow Process: A process during which a fluid flows through a control volume steadily.

Temperature and Pressure

• Temperature: A measure of hotness or coldness, measured in Celsius or Kelvin scales.
• Pressure: The force exerted by a fluid per unit area, measured in pascals.

Thermodynamic Equilibrium

• Thermodynamic Equilibrium: A system that exists in a state of equilibrium, with no changes in macroscopic properties observed if the system is isolated from its surroundings.

Quasi-Static Process and Reversible Process

• Quasi-Static Process: A process that is performed in an infinitesimally slow manner, with the system remaining in equilibrium at all times.
• Reversible Process: A process that is performed in such a way that both the system and surrounding can be restored to their initial state without producing any changes in the rest of the universe.

Irreversible Process

• Irreversible Process: A process that is carried out in such a way that the system and surrounding cannot be exactly restored to their respective initial states at the end of the reverse process.

Work in Thermodynamics

• Work: The transfer of energy that occurs when a force is applied to an object, causing it to move.
• Thermodynamic Work: Work involves energy transfer that occurs when a system undergoes a change in volume or pressure.
• Pressure-Volume Work: Work done by or on a system at constant pressure, given by W = PΔV.

Sign Convention and Heat Transfer

• Sign Convention: Work done by the system is positive, and work done on the system is negative.
• Heat Transfer: The transfer of energy from one body to another due to a temperature difference.