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Ideal Gases
K Warne
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Gas Problems – Aerosol cans
Question: Pressurized containers (aerosol cans) carry warnings to avoid
heating the container.
Why is this?
Describe a gas law that relates to this problem and explain it’s relevance
in terms of the Kinetic Theory of Gases.
NO!!!!
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Gas Problems• Explain how and why real gases differ from the behaviour
of an ‘ideal gas’.
Real gases deviate from the ideal gas model - this occurs at high pressure and low temperature.
1. At high pressure
• the particles are forced close together and their volume adds to the total volume of the gas.
• The volume of the real gas is larger than that of an ideal gas at high pressure.
2. At low temperature
• the forces between the particles pull them closer together.
• The volume of the real gas is therefore lower than that of an ideal gas.
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Gas Problems1. If a car tyre has a pressure of 280 kPa at 25o C, what
would the pressure be if the tyre temperature heats up to
38o C on a long journey? (Assuming the volume stays
constant.)
P1 = P2
T1 T2
280000 = P2
298 311
P2 = 260906 Pa
= 292.21 kPa (4)
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Temperature Scales• 0° Celsius = 273Kelvin
• ABSOLUTE ZERO 0
Kelvin = -273°C
• Celsius Kelvin
……………………
• Kelvin Celsius
…………………….
Convert to K:
Boiling point water 100o C
Room Temp 25o C
Body Temperature 37o
Kelvin Celsius Fahrenheit
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Macroscopic / microscopicKinetic theory relates the ________________ properties of substances
to its ___________________ properties.
Pressure= force/area
Volume =lxb h
Temperature = o C or K
Pressure: _________________ per unit _________.
Temperature: is a measure of the _____________________ of particles.
Macroscopic properties:
___________, ___________, ____________
Microscopic properties:
________ & ________ of particles
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Effect of Temperature - Guy Lussacs’ LawThe temperature of a fixed mass of gas is increased while the volume is kept
constant.
Guy Lussack's LawP (Pa) x103 T (K)
V = const
100 298.0
x1.4 120 357.6 x 1.4
140 417.2
160 476.8
180 536.4
x 2 200 596.0 x 2
The temperature is directly proportional to the pressure - if the pressure doubles the temperature
would also double.
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
0 50 100 150 200 250T
emp
era
ture
(K
)Pressure (Pa) x 103
T (K)
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Effect of Temp
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A weather balloon has a volume of 5 dm3 at sea level when the
temperature is 25o C. What would the volume of the balloon be if
the temperature rose to 35o C on a hot day?
Pressure - volume example.
Given: V1 = 5 dm3 T1 = 25 + 273 = 298 K T2 = 35 + 273 = 308K
Asked: V2
V1/ T1 = V2 /T2
(5/298) = V2 / 308
V2 = 308*(5/298) = 5.17 dm3
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Pressure & VolumeIf the __________ of a fixed mass of gas is _______
the _________ will increase. (T = const.)
The pressure increases
because…This happens
because there is
________ for the
particles to
collide with so
the ______ of
__________
with the sides of
the container
_____________
increases.
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Boyles Law
Spreadsheet
T = 298K
Volume vs Pressure for a fixed mass of gas (T = const)
10
15
20
25
30
35
40
45
50
55
55 75 95 115 135 155 175 195 215
Boyle's Law
Pressur
e (kPa)
Volume
(cm3)
200 15
150 17
118 21
96 27
80 35
69 42P 1/V
P = k (1/V)
pV = k
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Ideal Gas DeviationsReal gases deviate from the ideal gas model - this
occurs at __________________ and ___________________.
At high ___________________
• the particles are _____________ and their _____________ adds to the ____________ of the gas.
• The volume of the real gas is ______________than that of an ideal gas at high pressure.
P
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Ideal Gas DeviationsAt low ______________
• the _____________ between the particles pull them ___________ together.
• The volume of the real gas is therefore __________ than that of an ideal gas.
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Real Gases - Deviations Real gases deviate from ideal
behavior at low __________ and high ____________.
Many real gases ___________ under these conditions.
At low __ and low ___
Real gas particles are _______ ______ by attractive forces - they therefore exert _____ ___________.
Indicate these areas on the graph!
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Hi -
This is a SAMPLE presentation only.
My FULL presentations, which contain a lot more more slides and other resources, are freely
available on my resource sharing website:
www.warnescience.net(click on link or logo)
Have a look and enjoy!
WarneScience