Thermal Physics Unit T1 The First Law of Thermodynamics

Overview: This unit is the first in a series on Thermal Physics. It begins with a discussion of temperature and temperature scales and then procedes to thermodynamic variables and their relationship to temperature. It discusses the diffferent kind of transformations and specific heats, and finally introduces the relation between work and energy and the first law and some applications of this law.

F. W. Sears and G. L. Salinger, Thermodynamics, Kinetic Theory, and Statistical Thermodynamics (S&S) Chapt. 1 -Fundamental Concepts; Chapt. 2 - Equations of State; Chapt. 3 - The First Law of Themrodynamics; Chapt. 4 - Some Consequences of the First Law, but excluding Sections 2.9,2.10,3.3,3-5,3.12,3.13,3.14.

Comment: There is over one hundred pages to go through here, but note that some sections can be excluded. Try to get a feeling for the spirit of thermodynamics which describes complicated systems in terms of only a few macroscopic variables such a temperature, pressure and volume.

After completing this unit you should understand:

1. The distinction between heat and temperature.
2. Temperature scales and the meaning of temperature .
3. Thermosdynamic variables such as P and V..
4. Equation of state.
5. Meaning of isothermal, adiabatic and isobaric tranformations..
6. Relation of energy to work.
7. Specific heat capacity at constant P and constant V.
8. Properties of an ideal and a van der Waals gas.
9. The relation of the first law of thermodyamics to the conservation of energy.

Question: Describe qualitatively how the first law of thermodynamics can be applied to:

1. a book sliding on a horizontal table,
2. rubbing your hands to warm them, and
3. boiling a pan of water on an electric stove.

Problems:

Chapt. 2: Problems 11,21; Chapt. 3, Problems 1,14,27; Chapt. 4, Problems 1,11,22.

1. Normal body temperature is 98.6 degrees F. Convert this to centigrade degrees.
2. An insulated glass contains 100 g of water and 20 g of ice, both at odegrees C. A silver spoon (specific heat o.056 cal/g-K) wighing 30 g an at 100 degrees C is put into the glass. What is the temperature of the water after the system has reach equilibrium? Does any ice remain, and if so how much?
3. Calculate the difference in the temperature of water at the top and bottom of Victoria Falls (height 360 ft.) Assume no heat is lost or gained from the surrounding air.