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?
We can increase it 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 doesn’t change.
What is the first law of thermodynamics?
ΔU = Q - W
Change in internal energy = Heat added - The work done
What is the specific heat capacity of 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 that:
* Has molecules with negligible volume
* Collisions which are elastic
* Cannot be liquified
* Has no interactions between the molecules (except during collisions)
* Obeys the (ideal) gas laws (Boyles law, Charles’ law and Pressure law)
What is Boyle’s law?
Pressure is inversely proportional to volume, providing temperature is constant.
In an ideal gas, how would increasing the volume change the temperature of the gas, while the pressure remains constant?
As you increase the volume, you also increase the temperature.
Explain how increasing the temperature of a balloon, while keeping the volume the same will increase the pressure.
- As the temperature increases, the average kinetic energy increases.
- Therefore the particles are travelling at a higher speed on average
- There are also more frequent collisions
- Which means the particles would exert a greater force
- Which would cause a increased rate of change of momentum
- Therefore increasing pressure.
What is absolute zero?
At - 273℃
This is where objects have no/minimum kinetic energy.
What is Avogadro’s constant? (in words)
The number of atoms there are in one mole of a substance.
State an assumption of an ideal gas related to time?
The time for each collisions is negligible in comparison to the time take between collisions.
What is meant by the root mean square speed?
The square root of the mean of the squares of the speeds of the molecules.
What is Brownian motion?
- Brownian motion is the idea that very small objects have random motion in a liquid or gas due to random bombardment by the molecules in this substance
- This movement will be fractionally more on one side than the other so a force will push it for an instant as the net forces shifts directions
- This random motion is Brownian Motion and gives evidence for the existence of atoms
