Thermal Physics Flashcards
Thermal Equilibrium
Energy is transferred from a region of high temp to a region of low temp.
This will keep happening until temp is equal everywhere. i.e. No net transfer.
Kelvin scale
T(k) = Value in degrees + 273
Define Internal energy
How is it different in an ideal gas?
How can it be increased?
Sum of the randomly distributed kinetic and potential energies of all particles in a substance.
Except in an ideal gas where it is equal to the sum of the Ek of all its particles. (ideal gases have no potential so no intermolecular forces acting)
can be increased by:
- doing work (compressing gas)
- increasing temp
Specific Heat Capacity
Energy required to increase temperature of 1kg of a substance by 1K.
Specific Latent Heat
Energy required per 1kg of a substance to change its state whilst keeping the pressure constant.
1 Mole
Avogardo’s constant (N(A)) = 6.02x10^23.
Amount of substance which contains the same number of particles,
as there are atoms,
in 12grams of carbon 12.
number of Moles
n = Mass / Molar Mass
Number of particles
N = n x N(A)
Number of particles =
number of moles x Avogadro’s constant
Assumptions of kinetic theory of gases
- Large number of particles in a rapid random motion.
- Volume of individual particles is negligible in to that of the gas.
- All collisions are elastic and time spent in/during the collision is negligible to the time between collisions.
- Forces between particles are negligible except when colliding.
Boyle’s LAW
At a constant temperature, pV is constant.
p1V1 = p2V2
p is inversely proportional to V
name the 3 gas laws and the purpose they serve
- Boyle’s Law
- Charles’ Law
- Pressure Law
the gas laws describe the relationship between pressure, volume and temp.
what do the three gas laws state?
Boyle’s - When temp is constant, p is inversely proportional to Volume (pV = k)
Charles’ - When pressure is constant, volume is directly proportional to (absolute) temp.
Pressure - when V is constant, pressure is directly proportional to (absolute) temp.
What is ‘Brownian Motion’ and how is it observed?
Random motion of large particles in a fluid caused by collisions.
Observed by looking at smoke particles through a microscope.
Define ‘impulse’, what it’s equal to and how to use it to find pressure, p.
Rate of change of momentum.
Equal to FORCE EXERTED.
Divide by area of 1 wall to find p.
Step by step, what is the derivation of the KINETIC ENERGY MODEL.
- Change of Momentum of one particle to a wall and back = mu - (-mu) **= 2mu*.
- s=d/t —-> t= 2l/u
- Impulse = momentum/time
= mu^2 / l - impulse/area = pressure
- sum up p of all particles
- average of speeds multiplied by no. particles.
- consider all directions in 3D shape (pythagorus but with 4 values). C^2(rms) = 3u(rms)^2
Therefore, pV = 1/3 Nm(Crms)^2
