Thermal Physics Flashcards
What is internal energy?
The sum of the potential and kinetic energies of a system
How can you increase the thermal energy of a system?
By heating it up or doing work on the object
Explain the energy changes that occur during a change of state.
During change of state, the potential energy of the particles change but the kinetic energies don’t change
What equation can be used to determine the energy required to change the temperature of a substance?
Q = m x c x Δt
Give the equation to work out the energy for a change of state.
Q = m x l
What is the ideal gas equation?
p V = n R T
What is the first law of thermo dynamics?
ΔU = Q - W
Where Q is the heat added to a system and W is the work done by the system
What is the specific heat capacity of a substance?
The energy required to raise the temperature of 1kg of a substance by 1K
What is the specific latent heat of a substance?
The energy required to change the state per unit mass of a substance, while keeping the temperature constant
What is an ideal gas?
A gas in which it’s molecules do not interact with each other, are believed to be perfect spheres and the gas is monoatomic
What is Boyle’s Law?
Pressure is inversely proportional to volume, if temperature is constant
In an ideal gas, how would increasing the volume change the temperature of the gas, while the pressure remains constant?
As the volume increases, temperature increases in order for pressure to remain constant
Explain how increasing the temperature of a balloon while keeping the volume the same will increase the pressure.
- Temperature increases so average kinetic energy increases
- Particles are travelling at a greater average speed
- More frequent collisions
- Particles exert a greater force on area of balloon
- Increased rate of change of momentum
- Increasing pressure
What is absolute zero?
At -273.15ºC
When objects have no kinetic energy
What is Avogadro’s constant in words?
The number of atoms there are in one mole of a substance
True or false: ‘All collisions between particles and the wall are elastic’ is an assumption of an ideal gas?
True
State an assumption of an ideal gas related to time.
The time for each collision is negligible in comparison to the time between collisions
Describe three other assumptions of the ideal gas equation.
- Particles move randomly
- Particles follow Newton’s laws of motion
- No intermolecular forces act between particles
- Volume of the particles is negligible compared to the volume of the container they are in
What is meant by the rms speed (root mean square)?
The square root of the mean of the squares of the speeds of the molecules
What is Brownian motion?
The idea that molecules have random motion in a gas or liquid due to random bombardment by the molecules in the substance. This random motion is Brownian motion and gives evidence for the existence of atoms
