Thermal Expansion of Materials
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Questions and Answers

What is thermal expansion?

  • A decrease in the size of an object with a decrease in its temperature
  • An increase in the size of an object with an increase in its temperature (correct)
  • A change in the density of an object with a change in its volume
  • A change in the shape of an object with a change in its pressure

    • What happens to the average separation between the atoms in an object when it undergoes thermal expansion?

  • It becomes zero
  • It remains the same
  • It decreases
  • It increases (correct)

    • What is similar to the notion of thermal expansion?

  • A geometric transformation of an object
  • A topological deformation of an object
  • A photographic reduction of an object
  • A photographic enlargement of an object (correct)

    • What happens to the hole of a metal washer when it is heated?

    <p>It increases in size</p> Signup and view all the answers

    What is one of the intended learning objectives of this lesson?

    <p>To define what is meant by the thermometric property</p> Signup and view all the answers

    What is the ideal gas law used for?

    <p>To determine various properties of a gas</p> Signup and view all the answers

    What is the consequence of the change in the average separation between the atoms in an object?

    <p>Thermal expansion</p> Signup and view all the answers

    What is linear expansion an example of?

    <p>Thermal expansion</p> Signup and view all the answers

    What happens to the volume of most liquids, including acetone, when their temperature increases?

    <p>They increase in volume</p> Signup and view all the answers

    What is the unusual behavior of water near 0°C?

    <p>It contracts with increasing temperature</p> Signup and view all the answers

    What is the maximum density of water?

    <p>1.000 g/cm³</p> Signup and view all the answers

    What is assumed to be nonexistent in ideal gases?

    <p>Interatomic forces</p> Signup and view all the answers

    What is the advantage of using the ideal gas model?

    <p>It is simple to use</p> Signup and view all the answers

    What is the unit of Avogadro's number?

    <p>no unit (it is a pure number)</p> Signup and view all the answers

    What is the molar mass of helium (He)?

    <p>4.00 g/mol</p> Signup and view all the answers

    What is the relation between pressure and volume of an ideal gas at constant temperature?

    <p>Pressure is inversely proportional to volume</p> Signup and view all the answers

    What is the name of the equation that interrelates the variables of an ideal gas?

    <p>Gas Equation of State</p> Signup and view all the answers

    What is the purpose of the movable piston in the ideal gas experiment?

    <p>To vary the volume of the gas</p> Signup and view all the answers

    What happens to the radius of a hole in a piece of material when it expands thermally?

    <p>The radius of the hole increases</p> Signup and view all the answers

    What is the relationship between the change in dimension and the change in temperature for small expansions?

    <p>The change in dimension is proportional to the first power of the change in temperature</p> Signup and view all the answers

    What is the unit of the coefficient of linear expansion?

    <p>(ºC)–1</p> Signup and view all the answers

    What is the formula for the change in length of an object due to thermal expansion?

    <p>ΔL = αLiΔT</p> Signup and view all the answers

    What is the assumption made in the formula for linear expansion?

    <p>The expansion is sufficiently small</p> Signup and view all the answers

    What happens to the bolts in the poorly designed electronic device when it expands thermally?

    <p>They move farther apart</p> Signup and view all the answers

    What is the formula for the final length of an object after thermal expansion?

    <p>Lf = Li + αLiΔT</p> Signup and view all the answers

    What is the definition of the coefficient of linear expansion?

    <p>α = ΔL/LiΔT</p> Signup and view all the answers

    What is the primary purpose of the compression process in an automobile engine?

    <p>To prepare the air-gasoline mixture for ignition</p> Signup and view all the answers

    What is the compression ratio of a typical automobile engine?

    <p>9.00 to 1</p> Signup and view all the answers

    What is the purpose of the intake and exhaust valves in an automobile engine?

    <p>To remain closed during the compression process</p> Signup and view all the answers

    What is the result of compressing the gas in the cylinders of an automobile engine?

    <p>The temperature of the gas increases</p> Signup and view all the answers

    What is the initial pressure of the gas in the SAMPLE PROBLEM 4?

    <p>1.00 atm</p> Signup and view all the answers

    What is the final pressure of the gas in the SAMPLE PROBLEM 4?

    <p>21.70 atm</p> Signup and view all the answers

    What is the initial temperature of the gas in the SAMPLE PROBLEM 4?

    <p>27.0°C</p> Signup and view all the answers

    What happens to the volume of the gas in the cylinders during the compression process?

    <p>It decreases to 1/9.00 of its original volume</p> Signup and view all the answers

    What is the relationship between the pressure of a gas and its temperature when the volume of the gas is kept constant?

    <p>The pressure of the gas is directly proportional to its temperature.</p> Signup and view all the answers

    What is the equation that combines and summarizes the other gas laws?

    <p>PV = nRT</p> Signup and view all the answers

    What is the value of the Universal Gas Constant R?

    <p>8.314 J/mol ∙ K = 0.08214 L ∙ atm/mol ∙ K</p> Signup and view all the answers

    What is the value of Boltzmann's constant k_B?

    <p>1.38 × 10^(-23) J/K</p> Signup and view all the answers

    What is the ideal gas law often expressed in terms of?

    <p>The total number of molecules, N, present in the sample</p> Signup and view all the answers

    What is the relationship between the volume of a gas and its temperature when the pressure of the gas is kept constant?

    <p>The volume of the gas is directly proportional to its temperature.</p> Signup and view all the answers

    What is the significance of the value 22.4 L?

    <p>It is the volume of 1 mole of any gas at atmospheric pressure and at 0°C.</p> Signup and view all the answers

    What are the thermodynamic variables of an ideal gas?

    <p>P, V, and T</p> Signup and view all the answers

    Study Notes

    Thermal Expansion

    • Thermal expansion is the increase in size of an object with an increase in its temperature.
    • This is a consequence of the change in the average separation between the atoms in an object.
    • The notion of thermal expansion can be thought of as being similar to a photographic enlargement of an object.
    • As an object is heated, all its dimensions will increase, including the size of a hole in the object.

    Linear Expansion

    • Linear expansion is the increase in length of an object with an increase in temperature.
    • The coefficient of linear expansion, α, is defined as the change in length (ΔL) per unit original length (Li) per unit change in temperature (ΔT).
    • α has units of (ºC)–1.
    • The change in length (ΔL) can be calculated using the formula: ΔL = αLiΔT.

    Area and Volume Expansion

    • Area and volume expansion occur when the surface area and volume of an object increase with an increase in temperature.
    • The expansion of a cavity in a piece of material occurs in the same way as if the cavity were filled with the material.

    Ideal Gas

    • An ideal gas is a hypothetical gas that obeys the ideal gas law: PV = nRT.
    • The ideal gas law combines and summarizes the other gas laws, such as Boyle's Law, Charles' Law, and Gay-Lussac's Law.
    • R is the universal gas constant, with a value of 8.314 J/mol·K.
    • One mole of any gas at atmospheric pressure and at 0ºC is 22.4 L.

    Macroscopic Description of an Ideal Gas

    • The equation of state for an ideal gas is PV = nRT.
    • The ideal gas model can be used to make predictions that are adequate to describe the behavior of real gases at low pressures.
    • The amount of gas in a given volume is conveniently expressed in terms of the number of moles, n.
    • Avogadro's number (NA) is 6.022 x 10²³.

    Thermometric Property

    • The thermometric property is a measure of the thermal expansion of an object.
    • The coefficient of linear expansion (α) is used to calculate the change in length of an object due to a change in temperature.

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    Description

    The quiz is about the thermal expansion of materials, where the cavity in a material expands similar to if it were filled with the material, and the change in dimensions is proportional to the first power of the change in temperature.

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