Thermal Flashcards
Assumptions for kinetic energy theory model
Collisions with the wall are elastic
Time in contact with the wall is negligible
Volume of particles are negligible compared to container volume
Explain why the ideal gas equation cannot be derived in a similar way to
pV = 1/3Nmcrms^2
Gas laws are empirical laws of nature whereas kinetic laws arise from theory
Why is a soft iron core used in a transformer?
- iron core focused and directs the magnetic field from the primary to the secondary coil
- soft iron is used as it is easily magnetised
Formula for work done with pressure and volume
W = pΔV
Charle’s Law ratio
V1/T1 = V2/T2
Describe the energy transfers when a gas column’s volume decreases
Work is done on the gas to compress it, so energy is transferred to the gas. In order to maintain constant temperature, the gas must transfer an equal amount of energy to its surroundings in the form of heat.
Explain the relationship between pressure and the length of a gas syringe can be predicted using the kinetic theory for an ideal gas
- if length decreases then volume decreases
- therefore there are more particles per unit volume
- V is directly proportional to L as V = πr^2L
- Therefore a decreased volume increases the number of collisions per unit time
- Decreased volume causes the rate of change of momentum to increase
- this means there’s a greater force acting on the wall therefore greater pressure
State and explain what happens to the speed of molecules when the temperature of the gas increases
- the average speed of molecules increases with absolute temperature
- as the mean kinetic energy is proportional to temperature
- KE (mean) = 3/2 KT
Latent heat of vaporisation
Breaks some intermolecular forces
What happens during a change of state?
Some of the intermolecular / atomi bonds are broken
The kinetic energy of the particles remain the same
The potential energy of the particles increase
Equation linking workdone with pressure and volume
Workdone in expanding or compressing
W = p deltaV
Absolute zero can be interpreted in terms of the ideal gas laws or the kinetic energy theory
Using the Gas laws, it is the temperature when the volume or pressure extrapolates to 0. Or Using pV = nRT where pV is zero
Whereas using the kinetic energy, it is the temperature at which random motion stops and kinetic energy is zero.
Compare the mean kinetic energy of the argon and helium atoms in a mixture
In equilibrium and at the same temperature both gases have the same mean kinetic energy
Explain in terms of the kinetic theory model, why a pressure is exerted by the gas on a piston
Particles collide with the pistons walls and change momentum. There is a force exerted on the surface of the wall due to the rate of change of momentum. This force exerts a pressure on the piston as Pressure = F/A
