Chapter 9: Heat and Thermodynamics
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Questions and Answers

What is a defining characteristic of two objects that are in thermal equilibrium?

  • They are at the same temperature. (correct)
  • They have the same mass.
  • They have the same volume.
  • They are made of the same material.

    • What is the role of a thermometer in the context of the Zeroth Law of Thermodynamics?

  • It measures the amount of heat transferred between objects.
  • It defines the temperature of a body based on its color change.
  • It establishes thermal equilibrium between two objects.
  • It acts as the 'third body' that determines if other objects are in thermal equilibrium. (correct)

    • What is the significance of the Zeroth Law of Thermodynamics?

  • It defines the relationship between heat and temperature.
  • It defines the concept of thermal equilibrium. (correct)
  • It defines the concept of specific heat capacity.
  • It explains how heat flows from a hot object to a cold object.

    • What is the formula for molar heat capacity?

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

    Why are our senses unreliable for determining temperature?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is the formula for calculating the heat required to raise the temperature of a substance at constant pressure?

    <p>𝑄𝑃 = 𝑛𝐶𝑃 Δ𝑇 (B)</p> Signup and view all the answers

    How much heat is required to raise the temperature of 2 moles of O2 from 0°C to 100°C if 𝐶𝑃 = 29.5 𝐽Τ𝑚𝑜𝑙.𝐾?

    <p>5900 J (C)</p> Signup and view all the answers

    Which of the following is an operational definition of temperature?

    <p>Temperature is a physical quantity that can be measured using a thermometer. (B)</p> Signup and view all the answers

    How does heat flow between objects in thermal contact?

    <p>Heat flows from the object with higher temperature to the object with lower temperature. (A)</p> Signup and view all the answers

    What is the formula for calculating the change in internal energy of an ideal gas?

    <p>Δ𝑈 = 𝑄 − 𝑊 (B)</p> Signup and view all the answers

    What happens when two bodies, one hot and one cold, are brought into thermal contact?

    <p>The colder body will gain heat from the hotter body. (B)</p> Signup and view all the answers

    What is the formula for calculating the molar heat capacity at constant volume (𝐶𝑉) for an ideal monatomic gas?

    <p>𝐶𝑉 = 3𝑅 / 2 (C)</p> Signup and view all the answers

    What is the formula for calculating the molar heat capacity at constant pressure (𝐶𝑃) for an ideal monatomic gas?

    <p>𝐶𝑃 = 5𝑅 / 2 (B)</p> Signup and view all the answers

    What is the key principle behind the Zeroth Law of Thermodynamics?

    <p>Two objects in thermal equilibrium with a third object are also in thermal equilibrium with each other. (B)</p> Signup and view all the answers

    Which of the following is a valid statement about the molar heat capacity of an ideal gas?

    <p>The molar heat capacity is independent of the pressure. (B)</p> Signup and view all the answers

    How much energy is transferred when 1.00 kg of water at 25.0 °C is heated to 30.0 °C?

    <p>21000 J (D)</p> Signup and view all the answers

    What happens to the internal energy of a system when heat is added at constant volume?

    <p>It increases. (D)</p> Signup and view all the answers

    In an isothermal process for an ideal gas, what is the change in internal energy?

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

    What is the relationship between heat added (Q) and work done (W) in an isothermal process?

    <p>Q = W. (B)</p> Signup and view all the answers

    Which of the following describes an isochoric process?

    <p>A process at constant volume. (C)</p> Signup and view all the answers

    During an isobaric process, how is the work done calculated?

    <p>W = PΔV. (B)</p> Signup and view all the answers

    According to the First Law of Thermodynamics, what does ΔU represent?

    <p>The change in internal energy of the system. (B)</p> Signup and view all the answers

    If a system does 200 J of work on the surroundings and absorbs 500 J of heat, what is the change in internal energy?

    <p>300 J. (D)</p> Signup and view all the answers

    What characterizes energy in thermodynamic processes with respect to its conservation?

    <p>Energy is conserved in closed systems. (B)</p> Signup and view all the answers

    What is the main characteristic of the process AB?

    <p>Heated at constant volume. (B)</p> Signup and view all the answers

    What is the value of QAB for the process AB?

    <p>511 J (D)</p> Signup and view all the answers

    Which statement is true regarding process DA?

    <p>The temperature decreases to 200 K. (A)</p> Signup and view all the answers

    What is the internal energy change ΔU for process AB?

    <p>QAB (D)</p> Signup and view all the answers

    What is the pressure at point C during the heating process BC?

    <p>203 kPa (D)</p> Signup and view all the answers

    What is the process that occurs after AB?

    <p>Isobaric heating. (A)</p> Signup and view all the answers

    What is the volume of the gas at point C?

    <p>4 L (C)</p> Signup and view all the answers

    Which of the following best describes the work done (W) during the process AB?

    <p>W is zero since the volume is constant. (A)</p> Signup and view all the answers

    What is the energy transfer calculated for the water?

    <p>20,920 J (C)</p> Signup and view all the answers

    Which temperature difference is used to calculate the energy transfer for aluminum?

    <p>50.0°C (A)</p> Signup and view all the answers

    How is the mass of the aluminum block determined using the energy gained by the water?

    <p>By using the equation QAl = mAl Cp ΔT with known values (D)</p> Signup and view all the answers

    What is the mass of the aluminum block calculated from the energy transfer?

    <p>0.465 kg (D)</p> Signup and view all the answers

    Which of the following values is the specific heat capacity of water?

    <p>4184 J/kg°C (A)</p> Signup and view all the answers

    To find the energy transferred to aluminum when it has a temperature difference of 50.0°C, what must you multiply?

    <p>mass of aluminum and Cp of aluminum (A)</p> Signup and view all the answers

    What value must be calculated first to solve for the mass of the aluminum block?

    <p>Energy gained by water (C)</p> Signup and view all the answers

    If the mass of water is doubled, how does it affect the energy transferred to water?

    <p>It doubles the energy transfer (C)</p> Signup and view all the answers

    What is the formula used to calculate heat transfer through conduction?

    <p>$q = kA(T_1 - T_2)$ (D)</p> Signup and view all the answers

    If the thermal conductivity of a material is 0.030 W/m·K and the heat load is 500W, what is the thickness of the styrofoam insulation needed?

    <p>0.054 m (C)</p> Signup and view all the answers

    Which type of convection is driven by buoyancy due to temperature differences?

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

    What is the convective heat transfer coefficient range for gases?

    <p>25 to 250 W/m²·K (D)</p> Signup and view all the answers

    In the equation $q = hA(T_s - T_∞)$, what does $T_s$ represent?

    <p>The surface temperature of the object (A)</p> Signup and view all the answers

    When calculating heat transfer through a wall, how is area ($A$) defined?

    <p>The surface area exposed to the temperature gradient (B)</p> Signup and view all the answers

    What is the heat transfer rate when a plate at 100°C is cooled by air at 25°C with a surface area of 2 m² and a convective heat transfer coefficient of 10 W/m²·K?

    <p>200 W (B)</p> Signup and view all the answers

    What factors influence the convective heat transfer coefficient ($h$)?

    <p>Fluid temperature and density (B), Fluid velocity and surface roughness (C)</p> Signup and view all the answers

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    Study Notes

    Chapter 9: Heat and Thermodynamics

    • Thermodynamics is the study of the effects of work, heat and energy on a system.
    • A thermodynamic system is a definite quantity of matter contained within defined boundaries and everything outside of these boundaries are called the surroundings.
    • Systems can exchange energy with surroundings via heat and/or work.
    • Heat is the energy in transfer from a hot to a cold body.
    • Objects are in thermal contact if heat can flow between them.
    • Eventually, thermal energy will stop flowing between systems in contact when they reach thermal equilibrium.
    • This means the objects will be at the same temperature.
    • Temperature is a scalar quantity that has the same value for objects in thermal equilibrium.
    • It is an operational definition that tells us how warm or cold an object is.
    • A thermometer is an instrument used to quantitatively measure the temperature of a body.
    • The zeroth law of thermodynamics states that if objects A and B are each in thermal equilibrium with a third object C, then A and B will be in thermal equilibrium with each other if placed in contact.

    The Concept of Temperature and Heat

    • Temperature is a physical quantity that tells us how warm or cold an object is.
    • Qualitatively, temperature is based on our senses e.g. hot, warm, cold.
    • Our senses can be misleading and inaccurate.
    • An operational definition of temperature is required
    • A thermally isolated system will not exchange energy with the surroundings.
    • Using two isolated systems that are different temperatures gives us a way to define temperature.

    Thermal Energy (Heat) versus Temperature

    • Thermal energy (heat) is kinetic energy in transit due to a temperature difference.
    • Thermal energy is measured in calories or joules.
    • Any object above absolute zero has thermal energy.
    • Temperature is the average kinetic energy of particles, not the total amount of kinetic energy.
    • Temperature is measured in degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K)
    • Absolute zero is 0 Kelvin.

    Thermodynamic Systems

    • Open system: Matter and heat can cross the boundary.
    • Closed system: Matter cannot cross the boundary, but heat can.
    • Isolated system: Neither matter nor heat can cross the boundary.

    Work - Mechanical Energy Transfer

    • Work done by an expanding gas (change in volume):
    • W = -FAs = PA∆s = PAV
    • Work done depends on the thermodynamic process.
    • Work done is path dependent and equals the area bounded by a P-V curve (Pressure-Volume curve).

    Internal Energy of a Thermodynamic System

    • Internal energy of a system is the sum of all kinetic and potential energies of the atoms or molecules in the system.

    The First Law of Thermodynamics

    • The first law of thermodynamics is a statement of conservation of energy.
    • ΔU = Q - W (change in internal energy = heat - work).
    • If the volume is constant, and heat is added, the internal energy increases.
    • If work is done on the external world, and the system doesn't gain heat, the internal energy of the system will decrease.

    Tables - Signs and Q or W.

    • Summarising what 'Q positive' means and other key points.

    Processes in Thermodynamics

    • Isothermal process:
    • Takes place at constant temperature.
    • Adiabatic process:
    • No heat transfer.
    • Isobaric process:
    • Constant pressure.
    • Isochoric process:
    • Constant volume.
    • Any heat or work entering or leaving a system can be calculated based on thermodynamic processes.

    Other Processes in Thermodynamics

    • Reversible process: A series of equilibrium states.
    • Cyclic process: The initial and final states are the same.
    • The internal energy for closed cycles is always zero.
    • Work and heat in these processes depend on the process itself.

    Specific Heats for an Ideal Gas

    • Defined as the heat required to raise the temperature of 1 mole of a substance by 1°C, at constant pressure or constant volume.
    • Specific heats at constant pressure (Cp) and constant volume (Cv) must be measured at these conditions.

    Calculating Energy Transfer

    • Energy transferred is calculated using the equation Q= mCpΔT.
    • Work is a key term involved in energy transfer and depends on the process being used to transfer the energy.
    • Heat flow between objects can be determined.

    Modes of Heat Transfer

    • Conduction: Heat transfer through a solid or between solids in direct contact due to molecular collisions. It requires a temperature gradient.
    • Convection: Heat transfer due to the bulk movement of a fluid (liquid or gas). it is driven by buoyancy or external forces like fans.
    • Radiation: Heat transfer via electromagnetic waves, which doesn't require a medium. It depends on temperature and surface properties.

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    Phys 1011-Chapter 9 Heat and Thermodynamics PDF

    Description

    Explore the concepts of heat and thermodynamics in this quiz. Understand the definitions of thermal systems, thermal contact, and the laws that govern temperature and energy exchange. Test your knowledge on key principles such as thermal equilibrium and temperature measurement.

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