Gas Law Gas Law
CalcConcepts
ulations
STP &
Gas Law
Temp.
Demos
Conversions
SCUBA &
GreenHouse
Effect
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Final Jeopardy Question
Experiment: Student A begins boiling a cup of
water in Boston while Student B does the
same at the same time in Denver. Which
student’s water will boil first and WHY?
Back
Student B (in Denver) since the atmospheric
pressure is lower in Denver (higher altitude),
water here will boil first. The water in
Denver will not need to meet as high of an
atmospheric pressure as that in Boston.
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As you go down in elevation, what happens
to the atmospheric pressure and WHY?
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Pressure increases as elevation decreases
because the air is more dense at lower
elevations.
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What does John’s Law state and what is the
equation?
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As pressure goes up, temperature goes up
(and vice-versa) at constant volume.
P1 =
P2
T1
T2
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What is the equation for Boyle’s law?
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P1V1 = P2V2
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What does Charles’ Law state?
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At constant pressure, as temperature
increases, volume increases (and viceversa).
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A sample of gas has a volume of 23 mL at 39oC
and 890 mm Hg. This sample is cooled down
to 11oC and now has a volume of 150 mL.
What is the new pressure?
Back
Use the combined gas law since all variables are
changing…
P1V1 =
T1
P2V2
T2
890 mm Hg ( 23 mL)
312 K
P2 = 124.22 mm Hg
=
P2 (150 mL)
284 K
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A 50 L container is filled with a gas to a
pressure of 4.7 atm at 32oC. At what
temperature IN DEGREES CELSIUS will the
pressure inside the container be 3.5 atm
with a volume of 50 L?
Back
Volume is constant, so use John’s law.
P1 = P2
T1
T2
4.7 atm = 3.5 atm
305 K
T2
T2 = 227.13 K = -45.87 oC
Back
A gas occupies a volume of 34 mL at
21.8 oC. To what temperature (in Kelvin)
must the gas be raised to have a volume of
86 mL? Assume constant pressure.
Back
Pressure is constant, so use Charles’ law.
V1 = V2
T1
T2
34 mL = 86 mL
294.8 K T2
T2 = 745.67 K
Back
A balloon has a volume of 6L at 13.2 psi. If
the balloon was brought to a pressure of 9.3
psi, what would the new volume be (assume
constant temp).
Back
Temp is constant, so use Boyle’s law.
P1V1 = P2V2
13.2 psi (6L) = 9.3 psi (V2)
V2 = 8.52 L
Back
Whose law is being used in the following
situation…
A sample of gas in a flexible container
occupies 46.5 mL at standard pressure. What
volume will it take up if the pressure was
increased to 3 atm? Assume constant temp.
Back
Temp is held constant, so it is Boyle’s law.
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Convert 280.1 kPa to mm Hg.
Back
760 mm Hg x 280.1 kPa
101.3 kPa
= 2101.44 mm Hg
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What is the Kelvin value for absolute zero, and
what theoretically happens at this
temperature?
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ZERO Kelvin (0K), and everything stops moving
at this temp.
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What is 550K in oC?
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277 oC
K = 273 + oC
SO… oC = K-273
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What is 38.5 oC in Kelvin?
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311.5 K
K = 273 + oC
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What are the values for STP in kPa and torr?
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101 kPa and 760 torr
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Explain how a straw works – and DO NOT USE
THE WORD “SUCK”.
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When you inhale, your body takes in the air that is in a straw,
creating less pressure in the straw. Since the pressure in the
straw is less than the pressure outside the straw, the
atmospheric pressure PUSHES the liquid into the straw so you
can enjoy!
Thank heaven for atmospheric pressure!
Back
Explain the egg in flask demo. AND DO NOT
USE THE PHRASE “SUCKED IN”.
Back
In the egg demo, water was heated in the flask. Since temp increased
in the flask, the pressure also increased.
The flask was then taken away from the heat, and an egg was placed
on top.
The flask cools, so the pressure inside the flask decreased.
Since the pressure inside the flask decreased, the atmospheric
pressure outside the flask PUSHED the egg into the flask.
Back
A pressure apparatus that contains a sample
of gas at a fixed volume is first placed into a
container of hot water. It is then plunged into
a container of liquid nitrogen. What happens
to the pressure and why?
Back
This is an example of John’s law – when
temp goes down, pressure goes down.
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Explain why the Ivory soap expanded in the
microwave.
Back
Since temp increased, so does volume.
This is Charles’ law.
Back
What will happen to the volume of a balloon if
it is placed into a bell jar (vacuum pump) and
the pump is turned on.
Hint: in a bell jar, the pressure inside
decreases.
Back
The volume of the balloon will
increase. This is Boyle’s law… as P
decreases, V increases and vice
versa.
Back
What is the relationship
between pressure and depth as
you descend during a SCUBA
dive?
Back
Every 10 meters (or 32 feet) you
descend is an increase in 1 atm.
Back
What would happen if someone
ascended too quickly during a
SCUBA dive?
Back
The lungs of the diver can expand too
quickly and tear. Since pressure decreases
as you ascend, volume will increase
(Boyle’s law).
Back
What has caused an increase in
global warming (greenhouse
effect) over the past 100 years?
Back
Gases in the earth’s atmosphere absorb heat coming from
the earth’s surface and reflect it back to the earth. This
warms the earth.
Through our daily activities such as driving cars, using a BBQ
grill, using air conditioners and refrigerators, more gases are
emitted into the environment which increases global
warming.
Back
What is the relationship between the
solubility of a gas and depth of
descent?
Back
As you descend further (elevation
decreases), the solubility of a gas
increases. So, at deeper depths, you will
have more gas dissolved in your body.
Back
What is one characteristic of the
ozone layer?
Back
*absorbs UV light
*thin layer surrounding the earth
*depletion could increase the amount of UV
rays hitting the earth which could mean
increased mutations.
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If you are making pasta in Los Angeles and at
the same time, your best friend in Colorado
Springs is doing the exact same thing, whose
pasta will cook first and why?
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LOS ANGELES – the boiling point of water in Los Angeles is higher
than the boiling point of water in Colorado Springs. WHY?
Water boils when the vapor pressure equals the atmospheric pressure.
Because the atmospheric pressure in L.A. is higher than that in
Colorado Springs, so even though the water in L.A. will boil second, it
will have a higher temperature providing more heat. THUS, the pasta
in L.A. will be done first.
Back
This Jeopardy Game was Created by:
Sara Feltman, 5th Grade Teacher
Scott Elementary School
1999-2000 School Year
Revised: RLipkowitz
2000