Module 5 Chapter 1 - Thermal Physics Flashcards
What is the internal energy of a gas?
Internal energy is the sum of the kinetic and potential energies of all the particles in a gas.
What is the specific heat capacity of a mateiral?
The specific heat capacity is the amount of energy required to increase 1 kg of the material by 1 degree. From this it’s easy to derive Q = mcΔθ.
What are the units of specific heat capacity?
J kg-1 K-1.
What is the specific latent heat of a material?
The specific latent heat is the energy required to change the state of 1 kg of the material.
What are the units of specific latent heat?
Specific latent heat has the units J kg-1.
Converting from degrees to Kelvin:
Add 273.15 to convert to kelvin.
What is the ideal gas law (equation)?
The equation is pV = nRT, where R = 8.31 (ideal gas constant). This is equivalent to pV = kNT.
What is the Boltzmann constant?
The Boltzmann constant is 2/3 of the average kinetic energy of a molecule in a gas per kelvin.
What equation links number of molecules in a gas and the number of moles?
N = Na n, where Na is Avogadro’s constant.
What equation links Avogadro’s constant, the ideal gas constant and the Boltzmann constant?
k Nₐ = R
Equation for work done on an ideal gas:
W = P ΔV
Work done = pressure * change in volume
What is the molar mass of a molecule?
The mass of a mole of a substance, equal (in grams) to the relative molecular mass of the molecule.
What is Boyle’s law?
Boyle’s law states that the volume of an ideal gas of fixed mass is inversely proportional to its pressure exerted at a fixed temperature.
PV ∝ T, where T is constant.
What is Charles’ law?
Charles’ law states that the volume of an ideal gas of fixed mass is directly proportional to its temperature at a fixed pressure.
PV ∝ T, where P is constant.
What is Gay-Lussac’s Law?
Gay-Lussac’s Law states that the pressure of an ideal gas of fixed mass is directly proportional to its temperature at a fixed volume.
PV ∝ T, where V is constant.
What was Brownian motion direct evidence of?
Brownian motion was evidence of atoms existing.
How did Robert Brown first observe Brownian motion?
Robert Brown noticed that the paths of pollen in water were irregular.
What equation can be used to calculate the pressure a gas exerts on its container?
P = 1/3 ρ v^2. Note that v is the root mean square velocity of the molecules in the container.
Assumptions for the kinetic model of a gas:
- Large number of molecules in random, rapid motion particles.
- Atoms (or molecules) occupy negligible volume compared to the volume of gas.
- All collisions are perfectly elastic.
- Time of the collisions is negligible compared to the time between collisions .
- Negligible forces between particles except during collision.
Derive Eₖ = 3/2 kT from P = 1/3 pv².
P = 1/3 pv² P = 1/3 (Nm / V) v² 3PV = Nmv² Using PV = NKT: 3NkT = Nmv² 3kT = mv² 3/2 kT = 1/2 mv² Eₖ = 3/2 kT
What is the value of Avogadro’s constant?
Nₐ = 6.02 x 10^23 mol^-1
What is the value of the ideal gas constant?
R = 8.31 J mol^-1 K^-1
What is the value of the Boltzmann constant?
k = 1.38x10^-23 J K^-1 (derived from R / Nₐ)
