Thermal Physics Flashcards
Define absolute zero
? The lowest temperature that is theoretically possible ( at this temperature particles would stop vibrating and exert zero pressure
Define Charles law
? Volume is directly proportional to temperature (K) at a constant pressure
V1/T1=V2/T2
Define Boyles law
? Pressure is inversely proportional to volume at a constant temperature. (Isothermal Change)
A gas at very high temperatures does not obey this law.
P1V1 = P2V2
Define Lussac’s Law
? Pressure is directly proportional to temperature (K) at a constant volume
P1/T1 =P2/T2
Define internal energy
? Is the sum of the randomly distributed kinetic energies and potential energies of the particles in a gas.
Properties of ideal gases
? Particles have no potential energy
- all collisions are elastic
- point masses
- no change of state
Define specific heat capacity
? the energy required to raise the temperature of 1kg of a given substance by 1 Kelvin
Equation to calculate S.H.C
Q = mc (change) T
Unit: J/kgK
Define specific latent heat
? The energy required to change the state of a 1kg of a substance without a change in temperature.
Equation for specific latent heat
E =mL
Units: J/kg
Conversion between Kelvin and Celsius
-273 Degrees = 0K
What in the kinetic theory
? The molecules of a gas are in a state of constant motion in which the speed and the direction of each molecule is completely random.
Assumption of the kinetic theory
- The molecules of a particular gas are identical and in random motion
- The collisions between the molecules and between the walls of the container are perfectly elastic
- The volume of a molecule is negligible, compared to the volume of the container
- There are no intermolecular attraction between the molecules
- The time taken for a collision between two molecules is negligible compared with the time taken for the collisions between a molecule and the wall
Steps to derive the equation
- Find an expression for the change in momentum when the ball collides
- Find an expression for the force (Δmv/t) from point 1 to point 2
- Find an expression for the pressure (F/A) due to this force
- Multiply by N molecules (total number in the container)
- Substitute Crms for Vx using the equation earlier
Equation for ideal gas
PV/T = k
pV =nRT / pV =NkT
Can you explain why the temperature of a substance stays steady when it is changing state?
The energy is no longer used to increase the temperature but instead used to break bonds between the molecules. Increasing the potential energy
How do you calculate WD in a PV graph
WD = p (change in volume)
Area under the graph
Can you state which materials heat up and cool down the fastest?
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