Air & Gases Flashcards
Mixing ratio = …………./……….
Number of atoms or molecules in gas / total number of all atoms and molecules of all gases present
The mixing ratio is the ratio of…..
One substance to the quantity of all substances present in a sample.
The earths atmosphere is held above the surface, defying gravity by
The continual energy input of the sun
Water acts as an
Energy store in the atmosphere.
Water captures energy as
Radiation and stores and transports energy.
Water vapour is a
Greenhouse gas
Ozone absorbs
Uv radiation
Ozone ground mixing ratio is
5 - 30 ppbv
Ozone altitude mixing ratio is
6000 - 8000 ppbv
6 - 8 ppmv
CO2 absorbs
IR, preventing it from escaping into space - it is a GHG.
CO2 is responsible for natural
Acid rain
Aerosols absorb radiation and scatter light, they are
Clumps of many different atoms and molecules, such as dust particles.
Air is 78% nitrogen,
21% oxygen and 1% trace gases - water, co2, ozone.
Number density N/V is the
Number of particles per unit volume
Mass density is the
Mass per unit volume
Mass density equation
P = m/v
The perfect gas law equation
P = N/V k T
P = N/V k T - units…
P - pressure - Pa
N/V - number density - m ^3
k - Baltzman constant - 1.38 x 10 ^-23 J K ^-1
T - temp - K
The perfect gas law relates
Pressure, density and temperature
The SI unit for pressure is
Pascals - Pa
Pressure is proportional to number density (P=N/V), therefore
If the number of particles in the gas is doubled, so is the pressure.
1 bar = 10 ^5 Pa
1mbar = 10^-3 bar = 100 Pa = 1 hPa
Pressure is a measure of the
Push of gas
If an area is halved, the force remains the same,
But the pressure is doubled.
0 K = ‘C +
+ 273.15
Nothing is lower than
0 K
Force is the product of mass x acceleration
F = ma
Pressure is defined as
Force per unit area
P = F/A
F = ma - units
Mass - kg
Acceleration - m s ^-2
If forces are not balanced, the acceleration from high to low pressure occurs, this
Creates a flow of air - wind
For every force there is an
Equal and opposing force
If force is applied, the an object changes speed that is
Directly proportional to F
a = F/m
The SI unit of force is
Newton (N)
1 Newton =
1 kg m s ^-2
1 pa =
1 N m^-2
To obey the perfect gas law, if T rises and p cannot change then,
N/V must decrease.
Mass -
M = pV
1/2 mv^2 = mgh =
v = square root 2gh
The perfect gas law tells us that
Temp, number density and pressure are all directly proportional to one another.
Convert mass to N/V by
N/V = mass density /mass of typical air particle.
J m^-3 =
1 Pa
Stefan Boltzmann law:
R = A σ Τ^4
R - rate of energy emitted.
A - surface area.
σ - Stefans constant 5.67 x 10-8 W m-2 K-4
