Ideal Gases

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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