The Development of Thermodynamics
Recognition of Heat as Energy
- Aristotle considered fire to be one of the basic elements.
- Thomas Newcomen -- steam engine (1712)
- Only observation was that something flowed from hot objects to cold objects.
- James Watt -- a better steam engine (1769)
- The something was characterized as a fluid.
- Count Rumford -- the boring of cannons (1790’s)
- In Galileo’s time the fluid was referred to as “phlogiston” and considered to be
the soul of matter.
- Phlogiston was considered to have mass, and was driven out, or absorbed by an
object, in the process of burning
- Sadi Carnot -- heat engines (cycles)
- James Joule -- equivalence of work and heat (1840’s)
- Julius Mayer -- equivalence of all forms of energy -- conservation of energy (1842)
- Sometime in the seventeenth century the named changed to “caloric”
Details About Heat and Temperature
Philosophical Consequences of the First Law of Thermodynamics
- Heat refers to the amount of thermal energy
- If energy is conserved then there is only “so much if it”
- Temperature refers to the “concentration” of energy
(average kinetic energy per molecule)
- Energy is created (or exchanged) for work
- Other forms of energy -- Chemical, Electrical, Radiant, Nuclear, Mass
- Heat capacity (specific heat)
reflects the rate at which the temperature of a given substance changes when
heat (thermal energy) is transferred to or from the object
Bright Ideas………
- Mechanical equivalent of heat 1 cal = 4.1866 Joules
- The value of absolute zero ( -273o K)
- The law of conservation of energy holds for heat and extends the law of
conservation of mechanical energy
First Law of Thermodynamics
ΔEnergy = Heat - Work
- All forms of energy are equivalent