6.2 Thermal physics Flashcards
Define internal energy.
Sum of randomly distributed KEs and PEs of all particles within a body.
State the first law of thermodynamics.
Change of internal energy of a system is equal to the total energy transfered due to heat and work done.
What is the conversion from Celcius to Kelvin?
K=℃+273
(And to get to Celcius from Kelvin: ℃=K-273)
What is absolute zero?
Lowest possible temperature (0K or -273℃). A substance at 0K has minimum internal energy (no KE).
What happens, in terms of energy, during a change of state?
The potential energies of the particles change, but not the kinetic energies.
Define specific heat capacity.
Energ yrequired to change the temperature of 1kg of a substance by 1K without changing state.
(or by 1℃)
What is the equation for specific heat capacity?
What do the letters represent in this equation?
What is specific latent heat of fusion?
Energy needed to change state of 1kg of substance from liquid to solid without temperature change,
(Or from solid to liquid)
What is specific latent heat of vapourisation?
Energy needed to change state of 1kg of substance from liquid to gas without temperature change,
(or gas to liquid)
What is the equation for latent heat?
Where L is specific latent heat of fusion or vapourisation
What do the letters represent in this equation?
Draw a temperature vs time graph of liquid water changing state to vapour?
State Boyle’s law.
Pressure is inversely proportional to volume.
For constant temperature and amount of gas.
State Charles’ law.
Volume is proportional to absolute temperature.
For constant pressure and amount of gas.
State the pressure law.
Pressure is proportional to absolute temperature.
For constant volume and amount of gas.
Explain Boyle’s law, considering the gas particles in a decreasing volume.
For constant temperature and amount of gas.
- As volume decreases, distance between particles decreases
- Causing in collision rate to increase
- Resulting in increased rate of change in momentum
- Hence increasing force on container walls, and thus pressure increases.
Explain Charles’ law, considering the gas particles in an increasing volume.
For constant pressure and amount of gas.
- As temperature increases, particles gain KE
- Particles move faster (on average) and further apart to maintain constant pressure
- Hence increasing volume
Explain pressure law, considering the gas particles when the temperature decreases.
For constant volume and amount of gas.
- As temperature decreases, particles lose KE
- Particles move slower (on average), reducing frequency of collisions
- Resulting in reduced rate of change of momentum
- Hence reducing force on container walls, and thus pressure decreases
What are the Ideal Gas equations?
What do the letters represent in these equations?
Work is the work done on a gas, provided pressure is constant?
Define Avogadro’s constant.
In words
Number of atoms in 12g of Carbon-12
-OR-
Number of particles in 1 mole of a substance
Define molar mass.
Mass of 1 mole of substance.
Where m=mass of substance
What do the letters represent in this equation?
Define molecular mass?
The mass of one molecule of substance.
How is Boltzmann’s constant defined?
What do the letters represent in this equation?
How do we find the number of particles from moles?
What do the letters represent in this equation?
What is Brownian motion?
The continuous random movement of particles in a fluid.
What does Brownian motion occur?
The particles are being bombarded by continually moving fluid particles.
(For example: a smoke particle in air)
What is Brownian motion evidence of?
Atoms and molecules.
What are the kinetic theory assumptions?
ie the assumption for this equation
- Large number of particles
- Newton’s laws of motion apply
- Particles make elastic collisions with each other and the walls of the container
- The time taken for each collision is negligible compare to the time between collisions
- Particles have negligible volume compare to the container
- There are no forces acting between particles (except in collisions)
- Particles are in constant random motion
What do the letters represent in this equation?
What is the internal energy of an Ideal Gas?
The sum of KEs of the particles of the gas.
What are the equations for the average KE of a gas particle?
What do the letters represent in this equation?
What is the total KE of all the particles?
What do the letters represent in this equation?
