lecture 1 - gases Flashcards
gases can be composed of
molecules - O2 N2
atoms - He Ar
molecules and atom gases behave the same so we call them both
particles
physical properties of the three phases of matter
solid:
✅ condensed
❌ fluid
liquid:
✅ condensed
✅ fluid
gas:
❌condensed
✅fluid
what does a condensed phase mean
difficult to compress
solid, liquid
hard to clap ur hand when theyre stuck in cement or under water
easy to clap ur hands in air
what does a fluid phase mean
it flows easily
liquid flows easily and so does gas
liquid does not flow easily
phases of matter according to microscopic criteria
particle sep similar to particle size
particles translating relative to eachother
what does particle separation similar to particle size mean
is the distance between particles similar to the size of the particle
what does particles can translate relative to eachother mean
can particles move
phases and their microscopic criteria
sep as big as size
solid: ✅
liquid:✅
gas: ❌ gas particles can be very spaced out
translate relative to eachother
solid:❌
liquid:✅
gas:✅
solid particles cannot translate relative to eachother but they are still not stationary as they can still
vibrate
ideal gas assumptions
particles have 0 volume
no interparticle forces
these are untrue
why do the untrue ideal gas assumptions lowkey make sense tho
gas with low density: weak inter-particle forces
particle vol will be very small compared to the total volume (if density is low enough)
what is p
pressure
Pa
what is v
volume
m3
1L is how many dm3
1
1L = 1dm3
what is T
thermodynamic temp
in Kelvin
from c to k temp we must add
273.15
n is
number of moles
in mol
R is
gas constant
8.3145
what is R equal to
boltzman constant
and
avogadros constant
pressure is directly proportional to
1/V
volume is directly proportional to
T
V is directly proportional to
n
ideal gas equation
pv = nrt
obeyed by many low density gases
equation of state for ideal gases
p Vm = RT
Vm = molar volume (V/n)
Vm units: m3 mol-1
consequence of ideal gases
no matter the identity of the gas, they behave the same way.
properties are determined by moles and not identity of the gas
daltons law
total pressure of a mixture of gases is equal to the sum of each of their partial pressures
what is the partial pressure of a gas
the pressure it exerts if it was by itself in the same volume
ideal gas equation for 2 ideal gases
p tot = n tot (RT) / V
or
ptot = na (RT)/V + nb (RT)/V
partial pressure equation for a gas
pp a = xa x ptot
xa= mole fraction (na/ntot)
2 collisions between gas particles
elastic
inelastic
elastic collisions
conserve total kinetic energy
inelastic collisions
change total kinetic energy
both collisions conserve…
momentum
what type of collision do atomic gases usually have
elastic
conserve kinetic energy
what type of collisions do molecular gases usually have
inelastic
energy is usually converted to rotational or vibrational energy.
reverse can also occur: rotational and vibrational into kinetic when collisions occur
on average collisions are usually
elastic
what generates the pressure of a gas
its collisions with the vessel walls
sum of partial pressures for a mix of ideal gases
pressure of the mixture
ideal gas equation refers to all
low density gases
