Thermodynamics Basics Quiz
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Questions and Answers

What sign convention is used when energy leaves the system?

  • The sign is (-) (correct)
  • There is no sign convention
  • The sign is (+)
  • The sign is (±)
  • Which of the following statements about entropy change (ΔS) is true?

  • ΔS is negative when the system's order decreases.
  • ΔS is positive when the system's disorder increases. (correct)
  • ΔS is positive when the system's disorder decreases.
  • ΔS is negative when the system's disorder increases.
  • What is true when work is done on the system?

  • Work is the same as heat.
  • Work is positive. (correct)
  • Work is negative.
  • Work is an irrelevant factor.
  • What defines the relationship between internal energy change (ΔU) and work (w)?

    <p>ΔU = q + w</p> Signup and view all the answers

    In a closed system, which equation reflects the relationship when volume is constant?

    <p>ΔU = qv</p> Signup and view all the answers

    What is the sign of ΔH when a reaction is exothermic?

    <p>ΔH is negative.</p> Signup and view all the answers

    According to the first law of thermodynamics, what is true about the change in internal energy of the universe?

    <p>ΔUuniv = 0</p> Signup and view all the answers

    What happens in terms of energy when heat is added to a system?

    <p>Energy enters the system.</p> Signup and view all the answers

    Which type of system allows the transfer of both matter and energy?

    <p>Open system</p> Signup and view all the answers

    What distinguishes state functions from path functions in thermodynamics?

    <p>State functions are defined by final and initial values.</p> Signup and view all the answers

    In the context of thermodynamics, which of the following is considered an intensive property?

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

    What happens to temperature when combining two equal masses of water at the same temperature?

    <p>It remains the same.</p> Signup and view all the answers

    Which of the following correctly describes extensive properties?

    <p>They are additive and depend on the amount of material.</p> Signup and view all the answers

    Which of the following statements about path functions is true?

    <p>They include variables like heat and work.</p> Signup and view all the answers

    A bomb calorimeter is defined as which type of thermodynamic system?

    <p>Isolated system</p> Signup and view all the answers

    Which of the following is not a characteristic of intensive properties?

    <p>They are additive when combined.</p> Signup and view all the answers

    Which statement about the conservation of internal energy is true?

    <p>The internal energy of the universe is conserved.</p> Signup and view all the answers

    In the equation ΔU = q + w, what does 'q' represent?

    <p>The heat exchanged by the system.</p> Signup and view all the answers

    When the internal energy change (ΔU) is calculated to be 4 kJ, what can be inferred?

    <p>The system has gained energy.</p> Signup and view all the answers

    What is the correct calculation of ΔU when 500 kJ of work is done by a system and it releases 300 kJ of energy as heat?

    <p>-800 kJ</p> Signup and view all the answers

    Which of the following statements about endothermic reactions is accurate?

    <p>Energy enters the system, making ΔH positive.</p> Signup and view all the answers

    Given the equation for enthalpy change (ΔH = Hproducts - Hreactants), how would you classify a reaction with a ΔH of 50 kJ?

    <p>Endothermic reaction.</p> Signup and view all the answers

    What value of q implies that heat is given off by the system?

    <p>-50 kJ</p> Signup and view all the answers

    If a reaction releases 250 kJ of energy and does 500 kJ of work, what is the total change in internal energy?

    <p>-750 kJ</p> Signup and view all the answers

    Study Notes

    Open, Closed, and Isolated Systems

    • Open systems allow transfer of matter and energy
    • Closed systems allow transfer of energy, but not matter
    • Isolated systems do not allow transfer of matter or energy
    • Bomb calorimeters are examples of isolated systems due to insulation

    State Functions vs Path Functions

    • State functions describe the initial and final states of a system
    • State functions are calculated as "final - initial"
    • Example: Temperature change in taking water from room temperature to sun, then to the North Pole and back to room temperature
    • Path functions consider the pathway or mechanism in a given process
    • Examples: Heat (q) and work (w)
    • Example: Work (w) done pushing a box around a room depends on the path taken

    Extensive vs Intensive Properties

    • Extensive properties are additive
    • Examples: Volume, mass, moles, and energy
    • If you combine two buckets of water, the volume doubles
    • Intensive properties are not additive, they define a system
    • Examples: Temperature, density, and pressure
    • If you combine two buckets of water at 25 degrees Celsius the temperature remains at 25 degrees

    Thermodynamic Signs

    • The sign of a thermodynamic variable is negative if it leaves the system
    • The sign of a thermodynamic variable is positive if it enters the system
    • For example: When heat (q) leaves the system, the sign is negative
    • ΔG is negative for a spontaneous process and positive for a non-spontaneous process
    • ΔS is positive for increasing disorder and negative for increasing order
    • ΔH is negative for an exothermic process and positive for an endothermic process

    Heat vs Work

    • Heat is chaotic energy
    • Work is a concerted flow of energy that can be controlled
    • Both are path functions

    Internal Energy and Enthalpy Theory

    • The first law of thermodynamics states that ΔUuniv = 0, meaning energy is conserved
    • ΔU = q + w
    • U (internal energy) is a measure of all potential and kinetic energy in a system
    • Calorimetry measures unknown ΔU reactions using ΔUsys = -ΔUsurrondings
    • ΔH = ΔU + PΔV
    • In a closed system, ΔU = qv, because volume is constant (no PΔV work)
    • In an open system, ΔH = qp, because pressure is constant

    Calculating Internal Energy

    • Internal energy is calculated using the equation ΔU = q + w
    • For work: + indicates work is entering the system, - indicates work leaving the system
    • For heat: + indicates heat entering the system, - indicates heat leaving the system

    Energy Diagrams of Reactions

    • Energy entering the system indicates a positive ΔU
    • Energy leaving the system indicates a negative ΔU
    • ΔH = Hproducts - Hreactants
    • An increase in energy on the energy diagram is endothermic
    • A decrease in energy on the energy diagram is exothermic

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    Description

    Test your understanding of open, closed, and isolated systems, as well as state functions versus path functions. This quiz also covers extensive and intensive properties, providing a comprehensive overview of thermodynamic principles. Perfect for students in chemistry or physics.

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