Thermodynamics Quiz: Properties and Processes

Thermodynamics Fundamentals

• Thermodynamics is the science of the relationship between heat, work, and the properties of systems.
• It helps understand how to utilize these interactions beneficially.

Analogy

• Different currencies have different purchasing powers, similarly, various energy forms have differing values.
• Human civilization aims to harness different energy forms (shaft work, electrical energy, potential energy) to improve daily life.

Examples

• Examples of actions relating to thermodynamics include rising the temperature of water in a kettle, burning fuel to propel aircraft, cooling or heating a room, or keeping beverages cool.
• Related examples also entail generating electricity using coal/gas or petrol in car engines.
• Thermodynamics helps determine the best way to utilize the energy harnessed for various endeavors.

Definitions

• A system is a small part of the universe that is subject to thermodynamic laws.
• The system is often analogous to a free-body diagram in mechanics, where the laws of motion are applied.
• The system is a discernible collection of matter. Examples include a water kettle or an aircraft engine.
• Surroundings are the rest of the universe outside the system that affects it.
• Boundaries separate the system from the surroundings (e.g., walls of a kettle or an engine housing).

Types of Systems

• Closed system: Mass does not cross the system boundary. Heat and work can enter or leave. Mass is constant.
• Open system: Mass can cross the system boundary in both directions.
• Isolated system: There's no interaction between the system and its surroundings. No mass or energy transfer.

Choice of System and Boundaries

• System and boundary selection depends on the specifics of the problem.
• Boundaries can be real physical surfaces or imaginary ones for analysis.
• Example: the air in a room.
• The boundaries may move.

Macroscopic and Microscopic Approaches

• Macroscopic approach: Studying matter without considering molecular events. Focuses on observable quantities (pressure, temperature).
• Microscopic approach: Studying matter with a focus on molecular motion.

Property

• System characteristics assigned numerical values.
• These are macroscopic, not dependent on the system's history.
• Examples: weight, height.

Examples (Continued)

• Properties describe a system and are selected as needed.
• Choosing the best properties depends on the application.

Categories of Properties

• Extensive properties: Values depend on the system size (e.g., volume, mass).
• Intensive properties: Values do not depend on the system size (e.g., pressure, temperature).
• Specific properties: Extensive properties per unit mass (e.g., specific volume, density).

State

• A system's condition defined by its property values, giving a complete description.
• A change in one or more properties is a state change.

Phase

• A homogeneous part of a system with uniform chemical composition and physical structure (solid, liquid, vapor).
• Multiple phases form a heterogeneous system.

Path and Process

• The sequence of states during a state change is the path. A process is a series of state changes.
• Processes are often analogous to paths in a city (e.g., north–south, east–west).

Types of Processes

• Properties are often kept constant during processes (isothermal, isobaric, isochoric, isentropic, isenthalpic, isosteric, adiabatic).

Quasi-static Processes

• A quasi-static process is one in which the deviation from thermodynamic equilibrium is minimal.
• All states during the process are equilibrium states.
• Real-world processes are often, ideally, quasi-static.

Equilibrium State

• A system is in equilibrium if its properties do not change unless something in the surroundings is altered.
• Equilibrium generally requires uniformity of properties throughout.
• Equilibrium can be mechanical, thermal, phase, or chemical.

Types of Equilibrium

• Examples of equilibrium include pressure, potential, concentration of species, temperature.
• A thermodynamic system in equilibrium does not naturally perform work.

Definition of Temperature and Zeroth Law

• Temperature determines the degree of hotness.
• It is a relative term and often measures hotness compared to other systems in terms of their degree of heat.
• The zeroth law of thermodynamics describes systems that are in thermal equilibrium.

Zeroth Law (Continued)

• If two systems are in thermal equilibrium with a third, they are in thermal equilibrium with each other.
• This law underpins temperature measurements.

Explanation of Zeroth Law

• Temperatures of involved systems are constant during equilibrium.
• The zeroth law is essential for temperature measurement.

Units

• SI units (kilogram, meter, second, etc.) are used for various quantities.
• SI units for various parameters such as power, frequency, current, potential and magnetic parameters are defined and illustrated.
• Other units are also described for comparison. Pressure is expressed in pascals (Pa) or other units.

Units of Pressure

• Pressure is the force exerted on a unit area.
• The SI unit of pressure is the pascal (Pa).
• Various units for pressure are defined and examples are presented for further comprehension.

Units of Energy

• Energy is the capacity to exert force through distance (Newton-meter or Joule).
• Power is energy transfer or storage over time (watt).