Thermal Physics Flashcards
Define absolute zero
The temperature at which particles have no kinetic energy and the volume and pressure of a gas are zero
State Boyles Law
For a fixed mass of ideal gas at constant temperature the pressure is inversely proportional to the volume
State Charles Law
For a fixed mass of ideal gas at a constant pressure the volume is directly proportional to absolute temperature
State the pressure law
For a fixed mass of ideal gas at constant volume the pressure is directly proportional to the temperature
Define an ideal gas
A gas which obeys the 3 gas laws at all temperatures and pressures and cannot be liquefied (Collisions are all elastic and no intermolecular forces)
Define a mole of a substance
An amount of substance containing 6.02 x 10^23 particles
Define molar mass
The mass of one mole of a substance
What is Brownian motion
The random motion of particles in a fluid caused by the collisions with surrounding particles
Define pressure
The force per unit cross-sectional area
What causes pressure
Molecules applying a force to a surface
What is isobaric pressure
Constant pressure
What do the letters in pV=nRT represent
p = pressure V = volume n = number of moles R = molar gas constant T = temp in kelvin
What equation represents moles, molar mass and mass
m = nM mass = number of moles x molar mass
What happens to normal gas molecules
They undergo collisions with other particles, move at different speeds and move unpredictably randomly
Explain the increase of pressure when a gas is heated or compressed
Pressure is due to particles applying a force against a surface. This occurs at random. When a particle hits a surface there is a change in momentum
What happens in a system if the temp increases but the volume is constant?
Molecules travel faster so mean kinetic energy of molecules increase, momentum of the molecules increases, impacts are harder and more frequent, each collision transfers more momentums, more force per unit area on surfaces and therefore more pressure. So if temp increases, the pressure increases and the volume stays constant
What are the assumptions for an ideal gas?
- All molecules are identical
- Molecules move randomly
- Newtonian mechanics apply
- Volume of the gas molecules is negligible
- No intermolecular (electrostatic or gravitational) forces apply
- Collisions are all elastic and kinetic energy is conserved
- Molecules move in a straight line at constant velocity
What equation links all three laws
P₁V₁/T₁ = P₂V₂/T₂
Do ideal gases have potential energy?
No since there are no intermolecular forces
What equation do we use for internal energy of an ideal gas?
3/2 nRT
How do you convert moles to number of molecules
Multiple moles by the Avogadro constant
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