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Gases and Their Properties CH 11
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Gases and Their Properties
CH 11
Areas to Explore Gas Particles and Motion Gas Variables Manipulating Variables
Pressure and Volume
Pressure and Temperature
Volume and Temperature
Volume and Amount
Combining Gases
• Kinetic Theory – all matter is in motion
• The energy of moving objects (even electrons, atoms, molecules) is called Kinetic Energy.
Kinetic Molecular Theory
Top
Gases: Have mass. Are compressible. fill their containers Diffuse Gases can move through each
other rapidly. exert pressure
Pressure is dependent on Temp.
Top
Gas Variables Pressure
Temperature
volume
Pressure
• Pressure is force per unit area• Atmospheric pressure, or air pressure
– (mixture of gases) caused by gases in atmosphere colliding with each other.
• Air pressure lower at higher altitudes. Greatest at sea level.
• External Pressure vs. Internal pressure
area
forcepressure
Which shoes create the most pressure?Top
Temperature
• A measure of the average kinetic energy of the particles in a sample of matter• Does this mean it always relates
to HEAT?
• What happens when molecules STOP moving?
Temperature Always use absolute temperature (Kelvin) when working with
gases.
ºF
ºC
K
-459 32 212
-273 0 100
0 273 373
32FC 95 K = ºC + 273Top
Volume
• the space that a substance or shape occupies or contains.
• How do gases ‘have’ volume?
• Standard unit: L or mL
Top
Pressure and Volume
P
V
PV = k
Volume (mL)
Pressure (torr)
P·V (mL·torr)
10.0 760.0 7.60 x 103
20.0 379.6 7.59 x 103
30.0 253.2 7.60 x 103
40.0 191.0 7.64 x 103
• As Pressure of the surroundings is increased, FORCE on the system is increased. • This will push the molecules closer together,
decreasing volume
• As P increased, V decreased
• INVERSLY RELATED
Top
kT
V
V
T
Volume and Temperature
Volume (mL)
Temperature (K)
V/T (mL/K)
40.0 273.2 0.146
44.0 298.2 0.148
47.7 323.2 0.148
51.3 348.2 0.147
• At Constant pressure temperature increased makes the molecules move faster
• This will make them increase the space they occupy!
• As T increases, V increases• DIRECTLY RELATED
• : V1T2 = V2T1
Top
kT
P
P
T
Pressure and Temperature
Temperature (K)
Pressure (torr)
P/T (torr/K)
248 691.6 2.79
273 760.0 2.78
298 828.4 2.78
373 1,041.2 2.79
• At Constant Volume temperature increased makes the molecules move faster
• This will make them increase the force they exert!
• As T increases, P increases• DIRECTLY RELATED
Top
kn
V
V
n
Volume and amount of Gas
Gas Volume
(mL) Mass
(g) Moles, n
V/n (L/mol)
O2 100.0 0.122 3.81 10-3 26.2
N2 100.0 0.110 3.93 10-3 25.5
CO2 100.0 0.176 4.00 10-3 25.0
• At constant pressure and temperature, as the amount of gas is increased, the space it takes up will increase!
• Directly Related
Top
• Can we combine all the equations into ONE formula?
Top
Combining Gases• The total pressure of a mixture of
gases equals the sum of the partial pressures of the individual gases.
Ptotal = P1 + P2 + ... Top
