ME 266 Thermodynamics 1: Introductory Concepts
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Questions and Answers

What is a state in thermodynamics?

  • A system's path from one equilibrium to another
  • A type of flow process
  • A condition of a system at a specific point in time (correct)
  • A process that occurs at constant temperature

    • What type of process occurs when the temperature of a system changes?

  • Isothermal process
  • Isobaric process
  • Isochoric process
  • None of the above (correct)

    • What is a path in thermodynamics?

  • A state of equilibrium
  • A constant-pressure process
  • A series of states through which a system passes during a process (correct)
  • A type of flow process

    • What occurs when a fluid enters a control volume with a different state than when it exits?

    <p>A flow process occurs</p> Signup and view all the answers

    What is a cycle in thermodynamics?

    <p>A process that returns to its initial state</p> Signup and view all the answers

    What is a property in thermodynamics?

    <p>A characteristic of a system</p> Signup and view all the answers

    What is a quasi-equilibrium?

    <p>A state that is close to equilibrium</p> Signup and view all the answers

    What is a process in thermodynamics?

    <p>A change from one state to another</p> Signup and view all the answers

    What type of functions are heat and work classified as?

    <p>Path functions</p> Signup and view all the answers

    What is a characteristic of a property X?

    <p>Its change in value is independent of the path of the process</p> Signup and view all the answers

    What is the symbol for the change in the value of a property X?

    <p>dX</p> Signup and view all the answers

    What is the expression for the change in the value of a property X?

    <p>∫dX</p> Signup and view all the answers

    What is an example of an intensive property?

    <p>Temperature</p> Signup and view all the answers

    What happens when two or more systems with intensive properties are brought together?

    <p>The intensive properties are not summed</p> Signup and view all the answers

    What type of quantity is dependent on the path of the process?

    <p>Path function</p> Signup and view all the answers

    What is a characteristic of a path function?

    <p>Its change in value depends on the path of the process</p> Signup and view all the answers

    What is the term used to describe the pressure of a system measured relative to the atmosphere?

    <p>Gauge pressure</p> Signup and view all the answers

    What is the relationship between absolute pressure, gauge pressure, and atmospheric pressure?

    <p>Absolute pressure = Gauge pressure + Atmospheric pressure</p> Signup and view all the answers

    What is the force balance equation for the fluid element in the pressure variation with elevation?

    <p>F1 + W - F2 = 0</p> Signup and view all the answers

    What is the relationship between the pressure and the elevation of a fluid?

    <p>Pressure decreases with elevation</p> Signup and view all the answers

    What is the formula for the pressure variation with elevation?

    <p>P = ρgZ</p> Signup and view all the answers

    What is the term used to describe the measurement of pressure using a column of fluid?

    <p>Manometry</p> Signup and view all the answers

    What is the main distinction between a closed system and an open system?

    <p>The ability to exchange energy with the surroundings</p> Signup and view all the answers

    What is the zeroth law of thermodynamics related to?

    <p>The temperature of a system</p> Signup and view all the answers

    What is the statement of the zeroth law of thermodynamics?

    <p>If two systems are equal in temperature to a third, they are equal in temperature to each other</p> Signup and view all the answers

    What is the pressure at which the ice point exists?

    <p>101 kPa</p> Signup and view all the answers

    What is the primary function of a system boundary?

    <p>To separate the system from its surroundings</p> Signup and view all the answers

    At what temperature does water boil in Celsius?

    <p>100 oC</p> Signup and view all the answers

    What is a control volume?

    <p>A surface enclosing a volume of interest</p> Signup and view all the answers

    What is a property in thermodynamics?

    <p>A macroscopic characteristic of a system</p> Signup and view all the answers

    What is the lowest temperature possible?

    <p>-273.15 oC</p> Signup and view all the answers

    What is the temperature of Absolute Zero in Fahrenheit?

    <p>-460 oF</p> Signup and view all the answers

    What defines the thermodynamic state of a system?

    <p>The values of all thermodynamic properties</p> Signup and view all the answers

    What is a thermodynamic process?

    <p>A change in the system's thermodynamic properties</p> Signup and view all the answers

    What is the characteristic of Absolute Zero?

    <p>All atomic and molecular motion stops</p> Signup and view all the answers

    What is the temperature of water freezing in Kelvin?

    <p>273 K</p> Signup and view all the answers

    What is a path in thermodynamics?

    <p>A sequence of equilibrium states</p> Signup and view all the answers

    What is the difference between a cycle and a flow process?

    <p>A cycle is a sequence of equilibrium states, while a flow process is a continuous change</p> Signup and view all the answers

    Study Notes

    Introductory Concepts and Definitions

    • A system can be classified as closed, open, or isolated.
    • System boundaries may be drawn to reflect the type of analysis one wishes to perform.
    • A control volume is defined by a surface (real or imaginary) enclosing a volume of interest.

    Properties and States

    • A property is a quantifiable macroscopic characteristic of a system (e.g., mass, volume, density, pressure, temperature, etc.).
    • The thermodynamic state of a system is defined by the values of all of its thermodynamic properties.
    • A process occurs whenever a system changes from one state to another state.

    Types of Processes

    • Constant-temperature process: isothermal.
    • Constant-pressure process: isobaric.
    • Constant-entropy process: isentropic.
    • Constant-volume process: isochoric.

    Path and Point Functions

    • Path functions are quantities that are not properties of the system and depend on the path of the process undergone by the system (e.g., heat and work).
    • The change in the value of a property is independent of the path, hence: ∫dX = X2 - X1.

    Extensive and Intensive Properties

    • An intensive property is one that does not depend on the mass of the system (e.g., temperature, pressure, density, and velocity).
    • Intensive properties are not summed when two or more systems are brought together.

    Thermodynamic Pressure

    • The pressure of a system is usually measured relative to the atmosphere (gauge pressure).
    • Absolute pressure = Gauge pressure + Atmospheric pressure.

    Pressure Variation with Elevation

    • Pressure varies with altitude or depth: ∂P/∂Z = -ρg.

    Manometry

    • P = Patm + PHg.

    Temperature Scale

    • Temperature is a measure of molecular activity.
    • The zeroth law of thermodynamics states that if two systems are equal in temperature to a third, they are equal in temperature to each other.
    • The ice point and steam point are chosen to establish a temperature scale, with a number of subdivisions created between them.
    • The Kelvin scale is designed to go to zero at absolute zero, where all atomic and molecular motion stops.

    Important Reference Points

    • Water boils at 100°C or 373 K.
    • Water freezes at 0°C or 273 K.
    • Absolute zero occurs at 0 K or -273.15°C or -460°F.

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    Description

    Learn about the fundamental concepts and definitions in thermodynamics, including systems, surroundings, and boundaries. This quiz is designed for ME 266 students at Kwame Nkrumah University of Science and Technology.

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