PHYS20064 Thermodynamics Lecture 1
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Questions and Answers

What distinguishes an intensive property from an extensive property?

  • Intensive properties depend on the amount of substance present.
  • Extensive properties are independent of the amount of substance present.
  • Extensive properties include temperature and pressure.
  • Intensive properties do not change when the mass of the system changes. (correct)

    • Which condition describes a system in thermal equilibrium?

  • The pressure varies at different points in the system.
  • There is a temperature gradient within the system.
  • The temperature is consistent throughout the entire system. (correct)
  • All phases of the system are at different temperatures.

    • How is gauge pressure defined?

  • It represents the absolute pressure in a vacuum.
  • It is the pressure relative to atmospheric pressure. (correct)
  • It measures only the atmospheric pressure.
  • It is the total pressure exerted by a fluid.

    • What signifies a system is in mechanical equilibrium?

    <p>The pressure remains unchanged at all points over time. (A)</p> Signup and view all the answers

    Which statement is true regarding absolute pressure?

    <p>It starts from the datum of absolute zero pressure. (D)</p> Signup and view all the answers

    Which of the following properties is considered an extensive property?

    <p>Volume (B)</p> Signup and view all the answers

    What does specific volume represent?

    <p>The volume occupied by a unit mass of the substance. (D)</p> Signup and view all the answers

    Why does a system in equilibrium experience no changes when isolated?

    <p>There are no unbalanced potentials within the system. (B)</p> Signup and view all the answers

    What does Specific Gravity measure?

    <p>The ratio of the density of a substance to the density of a standard substance (A)</p> Signup and view all the answers

    Which mode of heat transfer involves the movement of molecules?

    <p>Convection (C)</p> Signup and view all the answers

    What is the Latent Heat of Fusion for ice at its melting point?

    <p>334 kJ/kg (B), 80 cal/gm (C)</p> Signup and view all the answers

    Which term best describes heat necessary to change the temperature without changing the phase?

    <p>Sensible Heat (A)</p> Signup and view all the answers

    How is Total Heat calculated?

    <p>The sum of latent heat and sensible heat (B)</p> Signup and view all the answers

    What does Absolute Entropy measure?

    <p>The measure of disorder or randomness of the system (D)</p> Signup and view all the answers

    In the Ideal Gas Law, which variables are related?

    <p>Pressure, volume, and temperature of a gas (C)</p> Signup and view all the answers

    What components constitute Enthalpy?

    <p>Flow energy and internal energy (C)</p> Signup and view all the answers

    What does the term 'thermodynamics' derive from?

    <p>Greek words meaning heat and power of motion (D)</p> Signup and view all the answers

    Which type of thermodynamic system allows mass to cross its boundary?

    <p>Open System (B)</p> Signup and view all the answers

    In a closed thermodynamic system, what can cross the boundary?

    <p>Heat and Work (C)</p> Signup and view all the answers

    What is an Isolated System characterized by?

    <p>Neither mass nor energy crosses the boundary (B)</p> Signup and view all the answers

    Which of the following correctly describes a property of a thermodynamic system?

    <p>A quantity describing the internal energy state (B)</p> Signup and view all the answers

    What is the primary function of thermodynamics in physics?

    <p>To convert one type of energy to another (C)</p> Signup and view all the answers

    Which statement accurately reflects a key aspect of a thermodynamic system?

    <p>It is a definite quantity of matter within a boundary (B)</p> Signup and view all the answers

    What does thermal efficiency measure in thermodynamics?

    <p>The effectiveness of energy conversion (C)</p> Signup and view all the answers

    What does Boyle's Law state about the relationship between pressure and volume at constant temperature?

    <p>Volume decreases as pressure increases. (B)</p> Signup and view all the answers

    Which equation represents Charles' Law?

    <p>V/T = constant (D)</p> Signup and view all the answers

    In Gay-Lussac's Law, what is held constant while pressure and temperature are related?

    <p>Volume remains constant. (A)</p> Signup and view all the answers

    What is the total pressure of a gas mixture according to Dalton's Law of Partial Pressure?

    <p>The sum of the partial pressures of the component gases. (A)</p> Signup and view all the answers

    Under standard conditions (STP), what is the temperature in Kelvin?

    <p>273.15 K (C)</p> Signup and view all the answers

    According to Avogadro's Law, what is true about equal volumes of gases under the same conditions?

    <p>They contain the same number of molecules. (A)</p> Signup and view all the answers

    The Combined Gas Law is represented by which equation?

    <p>P1V1T1 = P2V2T2 (A)</p> Signup and view all the answers

    What happens to the volume of an ideal gas when its temperature is raised at constant pressure?

    <p>The volume increases. (A)</p> Signup and view all the answers

    Study Notes

    Course Information

    • Course: Physics 2 (PHYS20064)
    • Lecture: 1
    • Institution: Polytechnic University of the Philippines
    • Department: Electronics Engineering (ECE)

    Learning Objectives

    • Define thermodynamics and identify different thermodynamic system properties
    • Understand different states of a system and its equilibrium
    • State the First Law of Thermodynamics and define heat, work, thermal efficiency, and different forms of energy
    • Identify and describe energy exchange processes involving various forms of energy, heat, and work
    • Apply the steady-flow energy equation or the First Law to assess heat, work, and energy balances in thermodynamic components (e.g., heaters, coolers, pumps, turbines, pistons)

    Thermodynamics

    • Derived from Greek words "Therme" (heat) and "Dynamis" (power of motion)
    • Branch of physics concerning energy conversions and their effects on temperature, pressure, volume, and mechanical action

    Thermodynamic System

    • A specific quantity of matter within a defined boundary
    • Surroundings: the region outside the system
    • Boundary: the real or imaginary surface separating the system from its surroundings (can be fixed or movable)

    Kinds of Thermodynamic Systems

    • Open System (Control Volume): Mass can cross the boundary
    • Closed System (Control Mass): Fixed mass, no mass transfer across the boundary, energy transfer (heat or work) is allowed
    • Isolated System: Neither mass nor energy can cross the boundary

    Properties of a System

    • Intensive Properties: Do not depend on the mass of the system (e.g., temperature, pressure, density, velocity)
    • Extensive Properties: Depend on the mass of the system (e.g., volume, momentum, kinetic energy)

    State and Equilibrium

    • State: System's condition at a particular instant, defined by its properties
    • Equilibrium: State of balance; no unbalanced potentials or driving forces within the system, no changes when isolated
    • Types of Equilibrium:
      • Thermal Equilibrium: Same temperature throughout the system
      • Mechanical Equilibrium: No pressure change within the system
      • Phase Equilibrium: System has multiple phases and each phase reaches equilibrium

    State Variables

    • Temperature: Intensity of heat, depends on the energy of the substance; Absolute Zero = Zero thermal energy; Temperature Scales: Celsius, Fahrenheit, Kelvin, Rankine.
    • Pressure: Force per unit area (measured in Pascal); Absolute Pressure (from zero pressure/perfect vacuum); Atmospheric Pressure (pressure from atmosphere's weight)
    • Gauge Pressure: Amount by which absolute pressure exceeds atmospheric pressure
    • Density: Mass per unit volume; Weight Density: Weight per unit volume
    • Specific Volume: Volume per unit mass

    Heat

    • A form of transferred energy arising from random molecular motion.

    • Modes of Heat Transmission:

      • Conduction: Heat transfer between molecules in contact
      • Convection: Heat transfer due to medium (fluid) motion
      • Radiation: Heat transfer without an intervening medium

    • Specific Heat: Heat needed to raise the temperature of a unit mass of a substance by 1°C

      • Q = mcΔT

    • Latent Heat: Heat to change phase without changing temperature

      • Q = ±mH (where H = latent heat of fusion/vaporization) -Use "+" if heat is absorbed (melting), "-" if heat is released (freezing)

    • Latent Heat of Fusion: Heat to change solid to liquid at melting point (e.g., ice melting)

    • Latent Heat of Vaporization: Heat to change liquid to vapor at boiling point

    • Sensible Heat: Heat to change the temperature of a substance without changing its phase. -Q=mcΔT

    • Total Heat: Sensible heat + Latent heat

    Enthalpy

    • Total useful energy of a substance (Internal energy + Flow Energy)
    • H = U + pV

    Entropy

    • Measure of energy unavailable to perform useful work in a specific environment.
      • Measure of randomness or disorder. -S = Q / T

    The Gas Laws

    • Ideal Gas Law: PV = nRT
      • P = Pressure, V = Volume, n = Number of moles, R = Universal Gas Constant, T = Temperature
    • Special Cases:
      • Boyle's Law (constant T, n): PV = constant
      • Charles's Law (constant P, n): V/T = constant
      • Gay-Lussac's Law (constant V, n): P/T = constant
    • Combined Gas Law: P1V1/T1 = P2V2/T2
    • Standard Conditions (STP): T = 273.15 K, P = 1.013 x 105 Pa or 1 atm
    • Dalton's Law of Partial Pressures: Total pressure of a mixture of gases is the sum of partial pressures of individual gases -Pt = P1 + P2 + ....+ Pn
    • Avogadro's Law: Equal volumes of gases under same conditions contain an equal number of molecules.

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    Description

    Test your understanding of the fundamental principles of thermodynamics as outlined in Physics 2. This quiz covers the definitions, concepts, and laws related to thermodynamic systems, energy exchanges, and the First Law of Thermodynamics. Assess your knowledge on how these principles apply to various thermodynamic components.

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