Thermal Physics Flashcards
(27 cards)
Define internal energy
The sum of the kinetic and potential energy of all the particles in a body
State 2 ways to increase the internal energy of a system
1) Do work on the system
2) Increase the temperature of the system
Describe the energy changes when a substances changes state
Internal energy changes, as potential energy changes while kinetic energy stays constant
Define specific heat capacity
The energy required to raise the temperature of 1kg of a substance by 1 degree Celsius, without changing its state
Define specific latent heat
The energy required to change the state of 1kg of a substance without changing its temperature
What do the gas laws describe
The experimental relationship between pressure, volume and temperature for a fixed mass of gas
Define Boyle’s law
At a constant temperature, pressure and volume are inversely proportional
State the equation for Boyle’s law
PV = k
State Charles’ law
At a constant pressure, volume is directly proportional to absolute temperature
State the equation for Charles’ law
V / T = k
State the pressure law
At a constant volume, pressure is directly proportional to absolute temperature
State the equation for the pressure law
P / T = k
Draw a graph to show the relationship between pressure and volume at a constant temperature
Draw a graph to show the relationship between volume and temperature at a constant pressure
Draw a graph to show the relationship between pressure and temperature at a constant volume
Describe a particles energy, volume and pressure at 0K
Particles have no kinetic energy
Volume and pressure of gas is zero
Write the derivation for the equation pV = N k T
- pV = nRT
- substitute n with N / Na
- replace R / Na with k, the Boltzmann constant
Write the equation for the wrok done on a gas to change its volume at a constant temperature
W = p x change in volume
How can you find the work done to change the volume for a gas graphically
Find area under graph of p vs V
What does the area under a graph of p vs V represent
Work done to change the volume of a gas at constant temperature
Describe Brownian motion
The random motion of larger particles in a fluid
Explain Charles’s law
Volume is directly proportional to absolute temperature at constant pressure
If temperature is increased, molecules gain kinetic energy, so move quicker, so at constant pressure move further apart, so volume increases
Explain the pressure law
Pressure is directly proportional to absolute temperature at constant volume
If temperature is increased, molecules gain kinetic energy so move quicker, so collide more frequently with container at constant volume, so pressure increases
Explain Boyle’s law
Pressure is inversely proportional to volume at constant temperature
If volume increases, molecules move further apart, so less frequency collisions, so pressure decreases
