Thermodynamics
I. Zeroth Law of Thermodynamics
If two or more objects of initially different temperatures are isolated from environment
they will eventually reach a common temperature,
which is intermediate between the temperatures of the hottest and coldest objects.
 
II. First Law of Thermodynamics
1.	Heat as a form of internal (thermal) energy Joule’s experiment: a glass of water can be heated up without any contact with a hotter object (hot plate),
but by doing certain amount of work on it (stirring water in the class).
Hence: heat is not a thermal fluid (caloric) but a form of internal (thermal) energy of an object,
which can be transferred due to difference in temperature.
Hence: there are two general ways to increase the temperature of a substance: 
	A.	By exposing it to something that has higher temperature (hot plate)
	B.	By doing work on it (stirring, friction, compression)
2.	Absolute (Kelvin) scale of temperature.
What determines the temperature of matter? Temperature of matter is a measure of the average kinetic energy of atoms and molecules of this matter.
The absolute (Kelvin) temperature is proportional to the average kinetic energy.
The absolute temperature is not measured in degrees, but in Kelvin units:
		TK=tºC+273.15
		tºC=(5/9)(tºF-32)
Does all motion stop at 0K? No, quantum motion remains. Exactly 0K is not attainable.
Peculiar properties of substances at low temperatures: superconductivity.
3.	Other forms of internal energy
Think: Ice melts at constant temperature of 273K. It means that matter possesses not only kinetic energy. 
Hence: Internal energy of a substance is the sum of the kinetic energies and potential energies
of all the atoms and molecules.
4.	Formulation of the First Law
The change of a substance’s internal energy equals the work done on it plus the heat transferred to it.  
			∆U=W(work)+Q(heat)
Conservation of energy principle!
 
III. Second Law of Thermodynamics
1.	Think about these facts
Fact 1: After a cold object and a hot object are brought into contact,
the cold one becomes hotter and the hot one becomes colder.
Fact 2: A sliding crate eventually stops,
but you never see an initially stationary object start to move all by itself.
Fact 3: If you drop an egg it splatters on a floor,
but a splattered egg never reforms and jumps up as a whole egg.
Fact 4: If you mix sugar with coffee in a cup, the sugar spreads throughout the cup,
but the individual sugar molecules will never clump up again into the shape of cubes.
Hence: Conservation of energy is not the only principle that governs the world.
Another principle: Irreversibility – reverse process is impossible.
2.	Formulation of the Second Law
Formulation 1: (R. Clausius):
No process is possible whose sole net result is the transfer of heat
from a lower to higher temperature.
Question: How does a refrigerator work?
Formulation 2: (Kelvin-Plank):
No device can be built that will repeatedly extract heat from a source
and deliver mechanical work or energy without losing some heat to a lower-temp reservoir.
Heat engine is a device that transforms heat into mechanical energy or work. 

Refrigerator is a heat engine in reverse.
Formulation 3: 
Entropy is a thermodynamic quantity that characterizes disorder in the system.
During any process in an isolated system the entropy always increases.