thermal physics - ideal gases Flashcards
what is Charles’s law?
for a fixed mass of gas at constant pressure, V ∝ T
what is the pressure law?
for a fixed mass of a gas at constant volume, p ∝ T
what is Boyle’s law?
for a fixed mass at constant temperature, V ∝ 1/p
what word describes a change that occurs under constant temperature?
isothermal change
what word describes a change that occurs under constant pressure?
isobaric change
what is “absolute zero”
in kelvin (a measure of temperature) zero degrees Celsius is 273 K
absolute zero is the coldest possible temperature, it is 0K or -273 degrees Celsius
how can absolute zero be determined experimentally?
find pressure of a gas as temperature varies
plot a graph of P against T (in degrees Celsius)
extrapolate the line backwards to find x intercept (should be -273 degrees/ 0K)
what is the ideal gas equations (give both versions)
pV = nRT
pV = NkT
what is the equation for number of moles?
n = m/Mr
what is the equation for the number of atoms in a given number of moles?
N = n x Na
what is the equation for the mass of 1 molecule?
m = Mr/Na
for an isobaric change, what is the equation for work done when work is done on/by a gas to change its volume?
ΔW = pΔV
if work is done on/by a gas, how can the work done be found from the p-V graph?
area under the graph
what word describes the fact that the gas laws came about from experimental data?
empirical
what is Brownian motion and how does it act as evidence for the existence of atoms?
large particles (e.g. smoke particles) undergo random motion when suspended in a fluid (e.g. air).
this can be explained by saying:
1. air is made us of molecules, and each smoke particle is being bombarded by molecules of the fluid - the collisions cause a resultant force on the smoke particle.
2. the air molecules must also move with random motion
3. air molecules are very small but have high speeds
