Specific Latent Heat Equation Quiz
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Questions and Answers

What happens to the temperature of a substance during the process of melting?

  • The temperature continuously rises until fully melted.
  • The temperature remains constant while energy is added. (correct)
  • The temperature decreases until it freezes.
  • The temperature fluctuates during melting.

    • What term describes the energy needed for a substance to change from a solid to a liquid?

  • Thermal energy
  • Latent heat of fusion (correct)
  • Latent heat of vaporisation
  • Specific heat capacity

    • What is indicated by the term 'latent' in latent heat?

  • The heat that affects temperature changes
  • The heat that is hidden and does not increase temperature (correct)
  • The heat required for raising temperature
  • The actual heat released during condensation

    • How does energy transferred to a substance during a phase change affect its molecules?

    <p>It helps overcome intermolecular forces.</p> Signup and view all the answers

    What occurs during the boiling point of a substance in terms of energy transfer?

    <p>The temperature remains constant despite energy being added.</p> Signup and view all the answers

    What is used to describe the energy required to change a substance from solid to liquid without changing its temperature?

    <p>Latent heat</p> Signup and view all the answers

    Which of the following statements is true about specific heat capacity?

    <p>It is the heat required to raise the temperature of 1 kg of a substance by 1 °C.</p> Signup and view all the answers

    During a heating process, what happens to the internal energy of a substance?

    <p>It increases as the temperature of the substance rises.</p> Signup and view all the answers

    What characterizes specific latent heat?

    <p>It is different for each substance and phase change.</p> Signup and view all the answers

    Which graph best represents the relationship between temperature and time during a phase change?

    <p>A curve that remains flat at the melting or boiling point.</p> Signup and view all the answers

    What is the formula to calculate the thermal energy required for a change in state?

    <p>E = mL</p> Signup and view all the answers

    How does pressure affect the phase of a substance according to the particle model?

    <p>Higher pressure can induce a phase change to solid.</p> Signup and view all the answers

    How much energy is required to melt 1 kg of ice, given the specific latent heat of fusion for water is 330 kJ/kg?

    <p>330,000 J</p> Signup and view all the answers

    What occurs at the molecular level when a substance absorbs latent heat?

    <p>Particles gain enough energy to break intermolecular bonds.</p> Signup and view all the answers

    If 0.60 kg of stearic acid is changing from liquid to solid, and the specific latent heat of fusion is 199,000 J/kg, what is the energy calculated using the equation E = mL?

    <p>119,400 J</p> Signup and view all the answers

    Which of the following is NOT a factor affecting internal energy?

    <p>Presence of a magnetic field</p> Signup and view all the answers

    What is the specific latent heat of vaporisation for water?

    <p>2.26 MJ/kg</p> Signup and view all the answers

    Which of the following statements is true regarding the energy required for state changes?

    <p>Vaporising requires roughly seven times more energy than melting.</p> Signup and view all the answers

    When rearranging the specific latent heat equation, which variable is solved for when you want to find the mass of the substance given energy and specific latent heat?

    <p>m = E/L</p> Signup and view all the answers

    What does the symbol L represent in the specific latent heat equation?

    <p>Specific latent heat</p> Signup and view all the answers

    What is the thermal energy required to vaporize 1 kg of water, given the specific latent heat of vaporisation is 2.26 MJ/kg?

    <p>2,260,000 J</p> Signup and view all the answers

    What is specific latent heat defined as?

    <p>Energy required to change state of 1 kg of substance without a change in temperature</p> Signup and view all the answers

    Which of the following correctly describes the specific latent heat of fusion?

    <p>Energy required to convert 1 kg of solid to liquid or vice versa</p> Signup and view all the answers

    What happens to the temperature of a substance during melting according to specific latent heat of fusion?

    <p>It remains constant until the phase change is complete</p> Signup and view all the answers

    Which statement correctly describes latent heat of vaporisation?

    <p>Energy needed to change 1 kg of liquid into gas at a constant temperature</p> Signup and view all the answers

    What is represented by the symbol L in specific latent heat?

    <p>Latent heat</p> Signup and view all the answers

    What is the effect of energy supplied during the phase change at the melting point?

    <p>Temperature remains constant during the phase change</p> Signup and view all the answers

    When does the latent heat of vaporisation occur?

    <p>When a liquid is vaporized or gas is condensed</p> Signup and view all the answers

    In what unit is latent heat expressed?

    <p>Joules per kilogram (J/kg)</p> Signup and view all the answers

    What is the scenario where the latent heat of fusion takes place?

    <p>Solid changing to liquid or liquid changing to solid</p> Signup and view all the answers

    Which statement is true regarding specific latent heat values during exams?

    <p>They are provided during the exam</p> Signup and view all the answers

    Study Notes

    Specific Latent Heat Equation

    • Energy ( E ) required to change the state of a mass ( m ) is calculated with the formula ( E = mL ).
    • Units: ( E ) is in joules (J), ( m ) in kilograms (kg), and ( L ) is the specific latent heat in joules per kilogram (J/kg).
    • Rearrangement of the equation can be visualized using a formula triangle.

    Values of Latent Heat for Water

    • Specific latent heat of fusion for water: 330 kJ/kg.
    • Specific latent heat of vaporisation for water: 2.26 MJ/kg.
    • Evaporating 1 kg of water utilizes approximately seven times more energy than melting 1 kg of ice to water.

    Worked Example

    • Energy required when 0.60 kg of stearic acid solidifies, using a specific latent heat of fusion ( L = 199,000 ) J/kg.
    • Calculation: ( E = 0.60 , \text{kg} \times 199,000 , \text{J/kg} = 119,400 , \text{J} ).

    Definition of Latent Heat

    • Latent heat signifies the energy needed to change the state of a mass without changing its temperature.
    • Two categories:
      • Specific latent heat of fusion: energy needed to change between solid and liquid states.
      • Specific latent heat of vaporisation: energy needed to change between liquid and gaseous states.

    Specific Latent Heat of Fusion

    • Defined as the energy to convert 1 kg of a substance from solid to liquid, or vice versa, at a constant temperature.
    • Temperature remains constant during melting or freezing until the entire mass transitions.

    Specific Latent Heat of Vaporisation

    • Defined as the energy to convert 1 kg of a substance from liquid to gas, or vice versa, at a constant temperature.
    • Liquid vaporisation maintains constant temperature until all substance is vaporized.

    Additional Insights

    • The energy transfers during phase changes occur at constant temperatures, leading to periods where temperature does not rise despite continued heating.
    • This "hidden" energy referred to as latent heat facilitates breaking intermolecular forces during state changes.
    • The concept of latent heat is essential for understanding energy transfers in physical changes of matter.

    Exam Tips

    • Remember to include the phrase "with no change in temperature" in the definition of specific latent heat for full credit.
    • Specific latent heat values are provided during exams; memorization is not necessary.
    • Use mnemonic devices to differentiate between fusion (solid to liquid) and vaporisation (liquid to gas) processes.

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    Description

    Test your understanding of the specific latent heat equation and its application to thermal energy changes. This quiz covers the formula E = mL, including key concepts like mass, energy, and latent heat values for water. Evaluate your grasp of these essential ideas in thermodynamics.

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