Laws of Thermodynamics

You can not subvert or change these laws:

The Zeroth Law (0): Systems are in equilibrium when they are at the same temperature.

• System is in it lowest energy state
• No energy can be extracted between two systems at the same temperature.
• All systems of different temperature in thermal contact will tend to equilibrium and therefore have the same temperature.
• Modeling Thermodynamic Equilibrium: (Warning, JAVA applets Page (might kill some browsers); Suggest using Netscape 4.04 or IE 4.0 for this. Netscape 3.0 might not completely work.)

0th Law: If A = B and B = C, then A = C

Thermal Equilibrium and Thermometers

If the objects are in Thermal Equilibrium NO Heat Energy will be transferred. If A is in thermal equilibrium with B and B is in thermal equilibrium with C the C will be in thermal equilibrium with A.

The First Law (1): Energy is Conserved in a closed system:

1st Law: Conservation of Energy:

or Heat Flow(Q) = Change in Internal Energy (U)(Change in Temperature) + Work (W)(something moves such as a piston) Class Demo: The Special Syringe

Suppose I took a syringe full of air but with a little bit of paper at the bottom. Suppose I rapidly pushed down on the plunger? What would happen? How is this process represented by the first law of thermodynamics? What can we say about the internal energy of the air in the syringe? What can we say about heat energy transfer?

Answer Here

2nd Law: Heat Flows from Hot to Cold

• The net flow of energy from a system is equal to the change in energy of that system
• We usually consider work and "waste" heat flow as the two kinds of energy

The Second Law (2) and The Law of Entropy:

• It is not possible to extract heat-energy from a reservoir and perform work without creating waste heat that does no work.
• The amount of disorder increases
• Things tend toward a state of randomness(this is not the same as chaos)
• You can not go from a disordered system to an ordered system without inputting external energy (this is a very important attribute of the second law)

  Example: We can do this
  
  100% of electrical energy converted to heat by pushing a current through a resistive stove element.

  We can not reverse the process. The stove element will not heat up and directly produce electricity.

  In the course of doing the original work we have increased the disorder to the system by heating it. In no way can we recover work of the disordered system without putting energy into the system.

To decrease local entropy requires work (energy).

• Your dorm room - it takes a lot of work to decrease the amount of disorder
• Iron Ore is originally concentrated in mountains - has a low disorder. Eventually it becomes mined and ends up distributed in the nations landfills.
• This combination of letters is readable and hence of low order but
  • ticmiainflteriraaladecolwrerdoohsobntoftrsdbne

  is not and would require a lot of work to rearrange into the previous sentence

Temperature: Measurement of Internal Energy...how fast molecules are moving or vibrating in gas, liquids & solids. Commonly called Kinetic Theory.

Measure Temperature in degrees Celsius.

0^oC ==> ICE

100^oC ==> Boiling Water

23^oC ==> Room Temperature (70^oF)

Kelvin Scale based on Absolute 0.

Absolute 0 ==> Temperature where all molecular motion stops.

Lecture Demonstration on Temperature Scale: Extrapolating Absolute Zero

Absolute Temperature K, Kelvin Scale

0K = -273^oC

0K = -460^oF

273K = 0^oC

Temperature in Kelvin = Temperature in degrees Celsius + 273

History of the Second Law