HeatEssentials - Heat:theEssentials...

Heat: the Essentials
Heat, Temperature, Specific Heat, Work
The first thermometer (Galileo’s) used expansion of gas with temperature: it wasn’t
reliable because it failed to allow for atmospheric pressure variation.
Mercury in glass became the standard, and made possible the discovery of the
Zeroth Law of Thermodynamics : If two objects are in thermal equilibrium with a
third, then they are in thermal equilibrium with each other. (The “third body” in a
practical situation being the thermometer.)
The unit of heat : 1 calorie is the heat required to raise the temperature of 1 gram of water
by 1 degree Celsius.
BUT the Calories labeling food items are KILOcalories : enough to heat one kilogram of
water through one degree!
The specific heat of a substance is the heat required in calories to raise the temperature of
1 gram by 1 degree Celsius.
And, you must be able to use this to solve simple calorimetric problems: finding specific
heat of a sample (as we did in class) by immersing it in boiling water for a while, then
transferring it to some cold water at a known temperature and finding the change in cold
water temperature.
Be aware of the result of Dulong and Petit, that for a whole series of elements the product of
atomic weight and specific heat was the same, and its significance in terms of heat capacity
per atom.