Week 20 (Jan. 6 - 10)

Reading: Temperature (Chap. 19)

Key Topics: temperature measurement, thermometry, thermal expansion, ideal gasses
Topics: The zeroth law of thermodynamics; thermometry; practical and absolute temperature scales; constant volume gas thermometry; ice, steam and triple points of water; Fahrenheit, Celsius and Kelvin temperature scales; thermal expansion coefficient; Boyle's and Charles' Laws; ideal gas law

Week 20 Homework Problems:
  1. Short essay questions for class discussion:
    • In principle, any gas can be used for a constant volume thermometer. Why can you not use oxygen below 15K? What gas might you use?
    • Metal lids to glass jars can often be loosened by running hot water over them. How is this possible?
    • Why should the amalgam used in dental fillings have the same average coefficient of thermal expansion as a tooth? What would occur if it didn't?
    • A mass is suspended from a rubber band. When the rubber band is heated with a hair drier, the rubber band shrinks and the mass is lifted. What does this imply about the coefficient of linear expansion of rubber?
    • Explain why a column of mercury in a glass thermometer first descends then rises when placed in a beaker of hot water.
    • Markings to indicate length are placed on a steel tape in a room that has a temperature of 22 deg. C. Are measurements made on a warm day, when the temperature is 27 deg. C too long, too short, or accurate? Explain.
    • The suspension of a pendulum clock is made of brass. When the temperature increases, does the period of the clock increase, decrease or remain the same? Explain.
    • Why don't ponds freeze all the way to the bottom in the winter?
  2. A constant volume gas thermometer is calibrated in dry ice (solid CO2 has a temperature of -80.0 deg. C) and in boiling ethyl alcohol (78.0 deg. C). The two pressures are 0.900 atm and 1.635 atm.
    • What value of absolute zero does the calibration yield?
    • What is the pressure at the freezing point of water?
    • The boiling point of water?
  3. A substance is heated from -12 deg. F to 150 deg. F. What is the change in temperature on the Celsius scale? The Kelvin scale?
  4. A hollow aluminum cylinder 20.0 cm deep has an internal capacity of 2.000 L at 20.0 deg. C. It is completely filled with turpentine, and then warmed to 80.0 deg. C.
    • How much turpentine overflows?
    • If it is then cooled back to 20.0 deg. C, how far below the cylinder's rim is the turpentine surface?
  5. An air bubble originating from a deep sea diver has a radius of 5.0 mm at some depth h. When the bubble reaches the surface of the water, it has a radius of 7.0 mm. Assuming the temperature of the air in the bubble remains constant, determine
    • the depth h of the diver
    • the absolute pressure at this depth
  6. Optional: A steel guitar string with a diameter of 1.00 mm is stretched between supports 80.0 cm apart. The temperature is 0.0 deg. C. The young's modulus of steel is 20e10 N/m^2 and the coefficient of linear is expansion is 11e-6 per deg. C.
    • find the mass per unit length of the string (assume the density of steel is 7.86e3 kg/m^3).
    • if the fundamental frequency f oscillation is 200 Hz, what is the tension in the string?
    • If the temperature is raised to 30.0 deg. C, find the tension and the fundamental frequency.
General College Physics