Paper 2: Thermal Physics Flashcards
Define Internal energy
Internal energy of a body is the sum of all kinetic energies and potential energies of all its particles.
How can internal energy increase?
- do work on the system
- increase the temperature of the system
Define Specific Heat Capacity
SHC is the amount of energy required to increase 1kg of a substance by 1K without changing its state.
Q = mcΔθ
Define Specific latent heat
Q = ml
SLH of a substance is the energy required to change a state of 1kg of material, without changing its temperature.
What does the gas laws describe?
the experimental relationship between pressure, volume and temperature for a fixed mass of gas.
What is Boyle’s Law?
if temperature is constant, pressure and volume are inversely proportional.
pV = k
What is Charles’ Law?
Charles’ Law -When pressure is constant, volume is directly
proportional to absolute temperature
V/T=k
What is the Pressure Law?
The Pressure Law -When volume is constant, pressure is
directly proportional to absolute temperature
p/T = k
How do you calculate moles of a substance?
Moles = Mass/RAM
What is Brownian motion?
is the random motion of larger particles in a fluid caused by collisions with surrounding particles
Explain Boyle’s Law using a simple molecular model
If you increase the volume of a fixed mass of gas, its molecules will move further apart
so collisions will be less frequent therefore pressure decreases.
Explain Charles’ Law using a simple molecular model.
When the temperature of a gas is increased, its molecules gain kinetic energy meaning
they will move more quickly and because pressure is kept constant (therefore frequency of
collisions is constant) the molecules move further apart and volume is increased.
Explain the Pressure law using a simple molecular model
When the temperature of a gas is increased, its molecules gain kinetic energy meaning
they will move more quickly, as volume is constant the frequency of collisions between
molecules and their container increases and they collide at higher speeds therefore
pressure is increased.
What are the assumptions of the kinetic theory model?
- No intermolecular forces act on the molecules
- The duration of the collisions is negligible compared to the time between collisions
- Motion is random
- Collisions are elastic
- motion of particles follows newtons laws
- molecules moves in straight lines
What is an ideal gas?
It has no other interactions between other particles other than its perfectly elastic collisions between them.
they do not have potential energy therefore all their internal energy is kinetic.
