## Classical Mechanics: Lecture 33 Notes

**Overview**

Today is a 52 minute lecture on gases. This is a great supplement to our chemistry work. I actually watched this one twice.

**Details**

In liquids, the molecules are almost touching one another. In gases, the molecules are far apart. This is why liquids are incompressible and gases are not.

PV = nRT

R = 8.314 J/K

T is temperature in degrees Kelvin

A mole always has 6.02 x 10^23 atoms/molecules/units. This is Avogadro’s number. A mole of any gas is 22.4 liters.

Protons are positive, electrons are negative, neutrons are neutral. Electrons have practically no mass. A nucleon is a neutron or a proton.

Atomic mass is the number of protons and neutrons.

Mass of a molecule = Atomic mass x 1.66 x 10^-27 kg

Molecules of gas are hitting a wall with average velocity v…

Momentum transfer for one collision= 2 mv

mv2 is independent of the mass of the molecule.

PV = NkT

N = total number of molecules

k = 1.38 x 10^-23 J/K = R/Na

Phase diagrams show states of matter as a function of temperature and pressure. Solids on the left, gases on the bottom, liquids in between.

Boiler’s Law = constant = PV

A fire extinguisher has radius 15 cm, height, temperature is 300K. The weight is 10 lbs is 4500 grams of CO2 is 100 moles. If this were a gas, the pressure would be 10^8 pascals or 1000 atm. It’s about 60 atm, 900 lbs/in2. The liquid and gas exist in equilibrium.

*Hydrostatic Equilibrium*

dP/dy = -dg

dP/dy = -Pmg/(kT)

Air weights roughly 29 grams/mole

Ph = Pi e^(-h/ho)

Put water into a paint can. Boil it. As the water boils, the pressure of water becomes 1 atm. The air will leave. Then close the top tightly, and the can will implode

**Review**

Electronegativity: NOF Cl Kr

Z eff = Z – S

PV = nRT

IGL : point source, random motion, elastic collisions, high temperatures, low pressure

(P + n2/a2) (V – nb) = nRT

Temperature Kelvin = T celsuis + 273

Momentum = mv

KE = K = mv2/2

PE = U = mgh

Noble gases: He, Ne, Ar, Kr, Xe, Kr

Atmospheric Layers: D E F1 F2