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Supercooling video...

Each degree of freedom contributes to the energy of the system

Monatomic—three degrees of freedom

Diatomic---five degrees of freedom

TnCE vint

nRT2

1

RCv2

3

RCv2

5

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Specific Heat of Various Materials

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Molar Specific Heat of Various Materials

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(R)

Molar Specific Heat of Various Materials

Two gases in separate containers have equal volumes, equal numbers

of molecules, and the same temperature. However, one gas is

monatomic and the other is diatomic. The pressure of the diatomic gas is

A. Less than that of the monatomic gas.

B. The same of that of the monatomic gas.

C. Greater than that of the monatomic gas.

Two gases in separate containers have equal volumes, equal numbers of molecules, and the same internal

energy Eint. However, one gas is monatomic and the other is diatomic. The pressure of the diatomic gas is

A. Less than that of the monatomic gas.

B. The same of that of the monatomic gas.

C. Greater than that of the monatomic gas.

Are you a weed?

Boltzmann’s distribution law

𝑛𝑉 𝐸 = 𝑛0𝑒−𝐸/𝑘𝐵𝑇

About how many gas molecules in this room are travelling at 200 m/s?

A. Less than 10

B. From 10 to 1,000

C. From 1,000 to 100,000

D. From 100,000 to 10,000,000

E. More than 10,000,000

Uses

Reaction barriers

Zeeman slowers

Atomic spectroscopy / Lasers

– How many atoms in a given state

– Doppler broadening

– Collision frequency

Quantum degeneracy

Suppose we have two jars of gas, one of helium and one of oxygen. If both jars have the same volume, and the two gases are at the same pressure and temperature, which jar contains the greatest number of molecules?

A. Jar of helium

B. Jar of oxygen

C. Both jars contain the same number.

Consider both gases to obey the ideal gas law. Also note

that the mass of an oxygen atom is greater than the mass of

a helium atom.

If you have equal numbers of heavy and light molecules in the

gas, the ones that move the fastest are:

A. The heavy ones

B. The light ones

C. They move at the same average speed

Escape speed is the speed an object has to go to escape Earth’s gravity. Escape speed for Earth is only 11.2 km/s.

A projectile leaving at a speed greater than 11.2 km/s will never fall back to the Earth.

If a gas molecule has a speed in excess of 11.2 km/s, it will escape totally from Earth. Hydrogen and helium have a mean speed that is a significant fraction of the escape speed. For this reason, there is almost no hydrogen or helium in Earth’s atmosphere.

Two identical containers hold equal amounts of the same gas at the same temperature. In each case, a piston compresses the gas to half the original volume. In one container the process

takes place adiabatically, and in the other container it takes place at constant temperature in contact with a heat reservoir. The

piston must do more work in the case of

(a) the adiabatic compression. (b) the constant-temperature compression. (c) In both processes the amount of work is the

same.