📜 Definitions:
Macroscopic: large quantities, measured in moles and grams
Equilibrium: state of balance, no net changes occurring
🗒️ Note: no system can perfectly reaches equilibrium
Functions of state or state variables: temperature, pressure, volume, composition, entropy, internal energy. It doesn’t dependent on the path taken
Equations of state: equations relating state variables in the case where they cannot be varied independently (ex $PV=nRT$)
Hysteresis: property of systems that do not reach equilibrium in a reasonable time.
Reversible: a process in which an infinitesimal change in the external conditions is enough to reverse the direction of the process
🗒️ Note: for a $PV$ plot, we assume a well pressure, which is not true if turbulence or shock waves from rapid piston movement
Macrostate: variables that define a macroscopic system in equilibrium
Microstate: description of the position and momenta of all the atoms in a system
🗒️ Note: Throughout the course we will assume quasi-equilibrium ( at any given time the system the system is in equilibrium )
💳 Take-away: Classical thermodynamics describes macroscopic systems in equilibrium in terms of a few measurable variables
<aside> <img src="https://prod-files-secure.s3.us-west-2.amazonaws.com/369dfa6b-d4d9-4cf2-a446-e369553b6347/76a58548-34e5-4cb3-846c-c39a650f4f49/Zeroth_law_of_thermodynamics.png" alt="https://prod-files-secure.s3.us-west-2.amazonaws.com/369dfa6b-d4d9-4cf2-a446-e369553b6347/76a58548-34e5-4cb3-846c-c39a650f4f49/Zeroth_law_of_thermodynamics.png" width="40px" /> Zeroth law of thermodynamics: if two bodies are separately in thermal equilibrium (constant temperature) with a third body (no heat flow between them when they are in contact), they are also in thermal equilibrium with one another. (they are at the same temperature)
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📜 Definition:
Thermoscope: body that changes visibly when heated, independent of any numerical scale
Thermometer: a calibrated thermoscope
Ideal gas or absolute temperature scale: in Kelvin $\rm K$, defined to be $\rm 273.16 \; K$ at the triple point of water
$$ T=\lim_{p\to 0}\frac{PV}{(PV)_\text{triple}}\times 273.16 \; \mathrm K $$
🗒️ Note: the limit is there as real gases approach ideal behaviour at 0 pressure, and the relation with the triple point of water was chosen so that the $\rm K$ matches the $\degree \rm C$, and the zero value is absolute zero
🗒️ Note: The symbol $T$ will always refer to absolute temperature
💳 Take-away: Absolute zero is the point at which thermal motion of an ideal gas vanishes
$$ \Delta E=Q+W \qquad \text dE=\text{d}\hspace*{-0.16em}\bar{} \,Q+\text{d}\hspace*{-0.16em}\bar{}\, W $$
Where $E$ is internal change,$E$$Q$ is heat added, $W$ is work and $\text{d}\hspace*{-0.16em}\bar{}$ is infinitesimal amount transferred
🗒️ Notes:
📜 Definition:
- Adiabatic process: $Q=0$
- Operating in a cycle: a system that return to its original state
- Reversible process: process that can be reversed without any net change in the system and the surroundings
- Isentropic process: without change in entropy, means adiabatic + reversible
🗒️ Note: in the case of an irreversible process (free expansion of a gas) it is necessary to find a reversible process linking the same initial and final states of the system
💳 Take-away: Energy can be transferred to a system by adding heat or doing work, but the net effect is the same
