THERMAL PHYSICS NOTES - rdarke

THERMAL PHYSICS NOTES

PHYSICS B4B

BAKERSFIELD COLLEGE Rick Darke (Instructor)

THERMODYNAMICS TERMS

thermodynamics - that branch of physics which deals with heat and temperature (also called thermal physics)

system - a definite quantity of matter enclosed by boundaries (real or imaginary)

open system - a system, into or out of which mass may be transferred

closed system - a system for which there is no transfer of mass across the boundaries

THERMODYNAMICS TERMS

temperature - an index of the average random translational kinetic energy of particles in a system; a relative measure of hotness or coolness

heat (energy) - the energy exchanged between objects because of a difference of temperature; a measure of the random kinetic energy of molecules in a substance

thermal contact - a condition in which heat may be exchanged between two objects

THERMODYNAMICS TERMS

thermal equilibrium - the condition in which there is no net heat exchange between objects in thermal contact

thermally isolated system - a system for which there is no transfer of heat energy across its boundaries

completely isolated system - a system for which there is no transfer of mass or heat energy across its boundaries (thermally isolated and closed)

HOW TO MAKE A THERMOMETER

STEP 1: Obtain a thermometric substance with some temperature response you believe to be a linear function of temperature.

example: liquid mercury. The volume of the mercury is a function of its temperature, and in a capillary of fixed diameter, the volume changes in mercury will be observable as height changes in the mercury column.

HOW TO MAKE A THERMOMETER

STEP 2: Create a temperature scale by defining two fixed-point temperatures.

example: Define the temperature of a water-ice equilibrium system at 1.0 atm to be 0?C. Define the temperature of a water-steam equilibrium system at 1.0 atm to be 100?C.

100?C 0?C

HOW TO MAKE A THERMOMETER

STEP 3: Create a graduated scale by

dividing the interval between the fixed-

point temperatures linearly into a num-

100?C

ber of divisions. This graduated scale

80?C 60?C

can then be extrapolated in both direc-

40?C 20?C

tions from the two fixed-point tempera-

0?C

tures.

P(atm) PHASE DIAGRAM OF H2O

218

1.00

fusion curve

solid (ice)

.006 sublimation curve

vaporiliquid zation (water) curve

triple point

gas (steam)

-273.15

0 .01 T(?C)

100 374

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