Thermodynamics

Table Of Contents

1 Zeroth Law of Thermodynamics

If temp of A=temp of B & Temp of B= Temp of C then temp of A=temp of C
Temperature is proportional to average kinetic energy.
Heat refers to the transfer of thermal energy from something hot to something cold
Kelvin Scales: absolute zero is the theoretical temperature where there is no thermal energy.
- Third Law states that the entropy of a perfectly-organized crystal at absolute zero is zero.
- F = 9/5 C + 32
- K = C + 273

A system is the portion of the universe that we are interested in observing or manipulating. The rest is called surroundings.

Isolated Systems: Not capable of exchanging energy or matter with their surroundings. Total change in internal energy must be zero.
Closed Systems: Capable of exchanging energy, but not matter with the surroundings.
- E.g – gas in vessels with moveable pistons
Open Systems: Can exchange both matter and energy with the environment.
State Functions: thermodynamic properties are a function of only the current equilibrium state. These are defined by the fact that they are path independent.
- E.g – Pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy
Process Function: describe the path taken to get from one state to another
- E.g. – Work and Heat

Just another iteration of the energy conservation law (energy cannot be created or destroyed).

Second Law of Thermodynamics: objects in thermal contact and not in thermal equilibrium will exchange heat energy.
Heat: defined as the process by which a quantity of energy is transferred between two objects as a result of difference in temperature.
- Unit is Joule, but can also be in calories (c), nutritional calories (C), and British thermal unit (BTU).
- One calorie is the amount og heat required to raise 1g of water by 1 degrees
- 1 Cal = 10^3 cal = 4184 J = 3.97 BTU

Conduction: direct transfer of energy from molecule to molecule through molecular collisions.
Metals are the best conductors while gases are the worst
Convection: transfer of heat by the physical motion of a fluid over a material. Only for liquids and gases since it needs the movement of a fluid.
Radiation: transfer of energy by electromagnetic waves. Can transfer energy through a vacuum.

Specific heat of a substance is defined as the amount of heat energy required to raise one gram of a substance by one degree Celsius or one-unit kelvin.
- Specific heat of water is 1 cal/(g*K) or 4.184 J/(g*K)
- q = mcΔT

Phase change occurs at a constant temperature since these changes are related to changes in potential energy and not kinetic energy.
Increasing the temperature of a substance undergoing a phase change will increase the potential energy which permits a greater number of microstates (ability to move).
- q = mL where L is the heat of transformation or latent heat
Liquid to solid is freezing/solidification; solid to liquid is melting/fusion and it occurs at the melting point and heat of transformation is called the heat of fusion.
Liquid to gas is boiling/evaporation/vaporization; gas to liquid is condensation and this occurs at the boiling point and heat of transformation is called the heat of vaporization.

Have three particular processes that are focused on isothermal, adiabatic and isovolumetric.
Thermodynamic processes can be showed on a P-v or T-V diagram.

Energy Dispersion: Energy goes from being concentrated to being spread out.
Entropy is a measure of how spontaneous a reaction will be.
- ΔS = Qrev/T
- ΔSuniverse = ΔSsystem + ΔSsurroundings > 0
Naturally Process: Something that intuitively occurs
Reversible Reaction: processes that can spontaneously reverse course. This only occurs when the system is always in equilibrium, as such an infinite time period would be needed.