# THERMODYNAMICS

I. We have to define the system - everything else is the surroundings

A. Describe the system using state coordinates - P = pressure; V = volume; M = mass; T = temperature

II. Two systems that have been in contact through a diathermic (conducting) wall for a long enough time that the state coordinates do not change are said to be in THERMAL EQUILIBRIUM (TE).

III. Zeroth Law of Thermodynamics - Two systems in TE with a third, are in thermal equilibrium with each other.

IV. Temperature - When two or more systems are in TE, they have the same temperature.

V. Temperature scales make use of a state coordinate and fixed points.

VI. Ideal gas temperature scale: T = [273.16]limp3->0(P/P3)V

where p3 is the pressure in a constant volume gas thermometer at the triple point of water and p is the pressure at the temperature T.

VII. Expansion

A. Volume expansion: = (1/V)(dV/dT)

B. Linear expansion: = (1/L)(dL/dT)

# SPECIFIC HEAT

I. The specific heat capacity: C = (1/m)(dQ/dT) where m = mass; dT is the temperature change; dQ is the heat energy added or removed

A. Heat is energy in transit due to temperature differences only.

B. Specific heat depends on the conditions under which it is measured

C. If the specific heat is temperature dependent, then we have to integrate.

II. What is a phase change and how is it related to a heat of transformation?

Example

Five hundred grams of water are in a copper calorimeter of mass 300 grams at an initial temperature of 15°C. A 560 gram piece of copper at a temperature of 100°C is dropped into the water. If the final temperature is 22.5°C, what is the specific heat capacity of copper?

# HEAT TRANSFER

I. Conduction: H = dQ/dt = -kA(dT/dx)

II. Convection: H = dQ/dt = -hA(dT)

III. Radiation: H = dQ/dT = seA(Th4 - Tc4)