https://youtu.be/kLqduWF6GXE

the flow of heat

heat motion

1800's industrial revolution, burning fossil fuels, factories, trains.

Svante Arrhenius was the first, in the late 1800's, to use basic principles of physical chemistry to calculate estimates of the extent to which increases in atmospheric carbon dioxide increase the Earth's surface temperature.

developed before discovery of atoms and molecules

0. defines temperature T. common sense law.

1. defines energy U. Energy conservation. You can break even. Convert heat into work with perfect efficiency. No waste.

2. defines entropy S. The direction of time. You can break even at 0 K. Above 0 K there is always waste.

3. numerical value assigned to entropy S. You can't get to 0 K.

Definitions

System - the part of the universe we are studying

Surroundings - everything else. when you are finished defining your system, what is left over is the surroundings.

Boundary - surface between the system and the surroundings, real or imaginary

system can be open, closed, or isolated

open - mass and energy flow through boundary.

isolated - neither mass nor energy can flow through boundary.

closed - energy can flow through boundary, mass cannot.

Examples of systems

human - open

water and ice in glass with a lid - closed

coffee and milk in thermos - isolated

a volume of air in a corner of the room - open

Describe the system

macroscopic properties, you only need a few variables

• p = pressure
• T = temperature
• V = volume
• n = number of moles
• m = mass

also, not considered in this lecture

• magnetic field
• magnetic susceptibiity
• electric field

homogeneous, like coffee and milk

heterogeneous, like water and ice

equilibrium - the properties do not change in time or space

in equilibrium or not. If not in equilibrium, it is not possible to describe the system with thermodynamic properties. Thermodynamics is concerned with systems in equilibrium.

number of components

glass of water - one component, H₂O, though heterogeneous

cup of latte - many components, though homogeneous

20:40

Extensive versus intensive properties

Extensive properties change along with the volume of the system. Intensive properties do not.

Extensive: V, m, n

Intensive: T, p, $\frac{V}{n}$ volume per mole

P, T, V, n, m are state variables. To fully describe a system in equilibrium you need n and two other variables.

Chemical notation

3 moles of hydrogen gas with a pressure of one bar at a temperature of 100 K
3H₂(g,1 bar, 100$^{\circ}$C)

5 moles of water + 5 moles of ethanol (100 proof vodka)
5H₂O (l, 1 bar, 25$^{\circ}$C) + 5CH₃CH₂OH (l, 1 bar, 25$^{\circ}$C)

an equilibrium state
3 moles of hydrogen gas, expansion (lower pressure, lower temperature
NOT a reaction
3H₂(g,5bar,100$^{\circ}$C) = 3H₂(g,1bar,50$^{\circ}$C)

Path

how to get from one state to the other
lower the pressure, lower the temperature

path can be

reversible or irreversible

adiabatic - no transfer of heat or mass between system and surroundings, ie, an isolated system

isobaric - constant pressure

isothermal - constant temperature

0th law, the common sense law, define temperature, put two objects together, the hot object A, the cold object B, heat flows from the hot object to the cold object, leaving a new object AB whose temperature is between that of A and B

[Why does the prof say the 0th law defines temperature?
He describes defining a thermometer, defining a temperature scale between reference points.
But he does not explain “define temperature”.]

in the 1800s, there were many temperature scales
originally Farenheit used human body temperature as reference point
common references points: freezing point and boiling point of water
Farenheit and others did not want common folk to have to use negative numbers to describe the weather, so if 32 is the freezing point of water, it is unlikely the weather temperature would ever get below 0

yeah