Kitchen Science

1
Putting Gases to Work
Instead of high-tech rocket or electromagnetic
forces, the jets are catapulted with the ancient
power source of steam.
2
ATOMS
Breaking the speed limit everywhere
3
Atomic World Fast and Furious
Helium
3,000 miles per hour
Air (oxygen nitrogen)
1,000 miles per hour
7,000,000,000
Helium atom is bouncing by using a custom motion
path set to repeat until end of slide.
collisions per second
4
So you see there is no such thing as still air.
The air molecules are constantly moving at an
average of 1,000 miles per hour.
5
Centuries ago it was known that the pressure in a
container could be increased dramatically by
heating water in it.
The animation is done with custom motion paths
(line type) to bounce balls off the walls.
Effect Options was used to set it to repeat.
6
Hero of Alexandria, Egypt
Hero's Engine
The first engine was created using water in a
heated container. An Egyptian named Hero
invented it.
7
Now when the water molecule strikes the front of
the chamber it pushes the vehicle slightly
forward. Normally, it may bounce to the back of
the chamber and cancel this effect. However, if
there is an opening then there will be no counter
push. The vehicle received a forward push
without the backward push because the molecules
are shooting out the nozzle without hitting back
of the chamber.
A later inventor figured he could propel a
vehicle using steam power in the same way the
Hero engine did. A common misconception is that
the exhaust does the propelling, but how can
steam that has left the container have any effect
on the chamber? They cant. As the water
molecules bounce around the chamber they strike
all sides imparting a small push (pressure) on
where it strikes.
8
Eventually someone tried to push a piston with
the pressure of steam. The piston was also
connected to a crankshaft to turn up and down
motion into circular motion. Unfortunately, when
the piston reached the top, the pressure
prevented it from coming back down.
The animation of the water vapor is done with
custom motion paths (line type) to bounce balls
off the walls. This animation is tricky
because other objects have to move at the same
time. The Start setting of the objects are set
to start With Previous. The top circle also
spins in step with the moving rod. The rod is
the trickiest because it moves and rotates at the
same time.
9
A solution was to add another chamber. With a
valve the steam can be released into a cool
chamber. The steam will condense to liquid
water. A vacuum will be left. A vacuum cannot
pull the piston down, but outside air pressure
can push it down.
The animation is similar to the previous page but
with a longer sequence. This animation is a bit
complicated so dont expect to follow it if you
are new to PowerPoint animations.
10
A more efficient design was to create steam in a
separate chamber and then introduce the high
pressure to the piston chamber as needed. Like
before, after the piston reaches the top, the
valve to the condenser is opened (not shown this
time)..
BOILER
CONDENSER
PISTON
11
Heres are some pictures of the steam engines
used in factories.
12
(No Transcript)
13
Heres a portable steam engine that could be used
around a farm.
14
The early steam locomotives were so novel that
they charged people to see them work.
15
Some inventors wanted the engine to propel a
vehicle that was both a boat and an automobile.
16
The steam locomotive was one of the most evident
ways we put steam pressure to work.
17
However, there was a new way to create pressure
and that was with a combustible liquid. It could
be ignited with a spark to produce gases of
carbon dioxide and water vapor. This was the
gasoline engine.
18
Gas Alteration of Latin chaos space, chaos
Date 1779
19
Article from 1897
The gas engine is one of the wonders of the 19th
century. Now, within three years of the 20th
century, it is a novel machine, eagerly sought by
many people. It is thought by persons who have
not studied its principles that it is a
steam-engine, using gas or gasoline as fuel for
the purpose of making steam. This is erroneous.
Gas and gasoline in specific proportion with air
are explosive material.
20

• In the next decade the steam engine will occupy
  the same relative position to the gas engine that
  the flint and steel now do to the lucifer match.

21

• the tallow dip to the electric light...

22

• ...the stage coach to the modern electric street
  cars, and civilization will record another grand
  stride toward the millennium.

23
The writer of that 1897 article knew gas engines
were much cleaner burning than the steam engines
that ran off of coal or wood. However, he didnt
realize we would pack so many of these gas
powered automobiles together. The pollution
again returned.
24
Perhaps hydrogen in the future will be our next
jump in clean burning fuel. We may choose to let
it ignite and provide pressure like current gas
engines or generate electricity using fuel cells
to power electric motors.
25
0
Seconds
9
00010203040506070809
Hits
18
½ volume
Pressure comes from the gas molecules hitting
the side of the container. Lets count them out
loud.
The bouncing molecules are done the same way as
before. This time I have a digital clock going
and a pressure gauge. The arrow on the gauge is
made with two arrows grouped, one is made
transparent. The spin effect makes it spin in
the middle.
26
VOLUME DECREASES
PRESSURE INCREASES
So we saw that as volume decreases the pressure
increases.
27
V0.5 , P2 V0.1, P10
V6 , P5 V3, P10
1
x P
V
P x
P
Mathematically when one value goes down as the
other goes up, we call it inversely proportional.

We can also show this by having them multiply by
each other.
28
27 ºC 300 K
0
Seconds
00010203040506070809
9
18
27 ºC 300 K
We saw that we can increase pressure by reducing
the volume, but we can also do it by increasing
the temperature and therefore the speed of the
gas molecules. At room temperature the hits are
1 hit/sec
0 K
29
327 ºC 600 K
327 ºC 600 K
0
Seconds
9
00010203040506070809
18
27 ºC 300 K
We are going from room temperature 27 ºC 300 K
to double that temperature, which is 600 Kelvin.
Lets count the number of collisions at this
higher speed. We get twice the number of
collisions and therefore twice the pressure.
The faster bouncing was easy. I just changed the
speed from slow (3 sec) to 1.5 sec. There is no
word for 1.5 sec. so you set it with the Timing
menu.
0 K
30
15 psi, 300 K
P
T
30 psi 3 psi
600 K 60 K
So we just saw that when temperature goes up, so
does the pressure. This makes sense because
higher temperature means the gas molecules are
going faster, colliding more often, and hitting
harder.
31
n moles
Pressure is proportional to the number of gas
molecules, which we count in moles.
Another way to increase pressure is to increase
the number of gas molecules. This is the
approach the steam engine used by heating water.
32
This animation is a copy of the previous ones,
but the sides of the container are separate lines
that can be flown outward at the same time with
an simultaneous explosion graphic (from
Autoshapes). The sound is added with Effect
options
This is also a safety problem. Any closed
container that has liquid in and gets heated will
likely increase pressure dramatically until the
container bursts.
33
P
T
V
V
V
n
This animation uses the Grow/shrink emphasis
effect. It also uses the transparency emphasis
effect. I like it because it helps show how
pressure and volume are related.
Lets review what we learned. If the volume
decreases the pressure will increase. Then the
reverse happens if the volume increases. The
pressure drops as gas molecules are farther apart.
34
T
P
V
V
n
The circle is drawn and the line type is set to
be dashed and it is set to be 6pt thick (Draw
tool bar). The circle uses the spin emphasis
effect. The top part of the circle is hidden
by a black box.
As we also learned, we can increase pressure by
introducing more molecules of the gas into the
volume.
35
P
T
V
n
1.4 x 1.4 2
doubles
We also learned that if temperature doubles, the
pressure doubles if volume is fixed. Or if the
container is flexible, the volume will double
with pressure staying constant. Or both can
increase such that the product of the two doubles.
1.5 x 1.33 2
36
R
P
T
V
n

• P is pressure measured in atmospheres.
• V is volume measured in Liters
• n is moles of gas present.
• R is a constant that converts the units. It's
  value is 0.0821 atmL/molK
• T is temperature measured in Kelvin.
• Simple algebra can be used to solve for any of
  these values.
• P nRT V nRT n PV T PV
  R nT
• V P RT
  nR PV

To make these quantities equal, we need a
conversion constant. We call it R (the Universal
Gas Constant)
37
This is where I play an excerpt from the radio
program Car Talk. In the recording the Car
Talk experts mentioned PVnRT when they were
explaining why the pistons on someones hatchback
wasnt working in the winter.
38
R
P
x1
T
1
V
n

1
x 0.0821

• Pressure1 atmosphere
• Volume1 Liter
• n 1 mole
• R0.0821
• What is the temperature?

Lets find what temperature the gas must be if we
have the following readings for these other
properties.
Normally 1 mole of a gas at 1 atmosphere pressure
takes up 22.4 liters. So it must be very cold to
only have a volume of 1 liter.
39
Frozen carbon dioxide(Dry Ice)
Dry ice can achieve high pressure in the way
water does when it turns into steam. However,
dry ice doesnt not need much heat. As it warms
up more CO2 will become gas causing a closed
container to explode.
This is a copy of the water animation. I just
changed the color of the liquid and spheres to
white.
40
Some people put dry ice in 2 liter bottles and
add a little water to warm the dry ice quickly.
They the put on the cap and throw the bottle out
the window. A few minutes later it explodes with
a huge boom! However, if the bottle explodes
early, this may happen
Maybe they should have learned PVnRT
41
What pressure could be reached when ¼ lb of dry
ice is placed in this 2 liter bottle? Temperature
that night was 86 F (30 C)
Facts2 Liter bottle ¼ lb 454 g 4 114g PV
nRT or P nRT
273 K
V
CO2 12g/mol 216g/mol 44 g/mol 114 g
mol
2.6
1 mol
44 g
42
What pressure could be reached when ¼ lb of dry
ice is placed in this 2 liter bottle? Temperature
that night was 86 F (30 C)
n R
T
2.6 mol x 0.0821 atmL x 303 K
molK
P
2.0 L
V
P 32.3 atmospheres
32.3 atm psi
475
14.7 psi
1 atm
A heavy duty tire will explode around 75 psi, so
we know this bottle is going to explode at 475
psi. Remember thats 475 pounds every square
inch. This bottle has about 50,000 lbs of total
force pushing outwards.
43
CONVERSIONS

• 760 mm of Hg
• 760 torr
• 29.9 in. of Hg
• 1 Atmosphere
• 14.7 lbs. per sq. in.
• Temperature conversions
• Kelvin Celsius 273
• OC (OF -32) x 5/9
• OF OC x 9/5 32

All Equal
Click on brown rectangles to popup an image.
Image will go away on its own. This is animation
that uses a trigger. It can make very
interactive screens.
44
Manometers
from Greek manos meaning sparse
45
sphygmomanometer

• sphygmometer
• Greek sphygmos meaning pulse (from sphyzein to
  throb)

Measures to 300mm Hg
46
This is the inner mechanisms of certain pressure
gauges.
47
When a pressure cooker is used, what causes the
increased pressure?
PVnRT PnRT V
Temperature goes from 25oC to 100oC Turn to
Kelvin by adding 273 to Celsius 297K to 373K
75K/297K25 increase in pressure
48
(No Transcript)
49

• You are on a camping trip and one tire has a slow
  leak. Finally it goes flat and you dont have a
  spare tire. You suggest crushing some of the dry
  ice you had brought along and funneling it into
  the tire through the tire valve. How many grams
  of dry ice would you need to blow up a tire with
  a volume of 80 liters and pressure of 32 psi?
  Current temp is 25OC.
• Change 32 psi to atm and 25OC to Kelvin
• 32 psi x 1 atm 2.177 atm
• 14.7 psi
• 25OC 27325298 K
• Solve PVnRT for n (moles) n PV
• RT
• n 2.177 atm x 80 Liters
• 0.0821 atmL/molK x 298K
• n 7.118 moles 7.118 mol x 44.01 g/mol
  313.3 g or 310 g
• 310 g x 1 lbs per 454 grams 0.68 lbs.

PVnRT
50
P1V1n1RT1 P2V2n2RT2 n1T1 n1T1
n2T2 n2T2
P1V1 R P2V2 R n1T1
n2T2
P1V1 P2V2 n1T1 n2T2
We can take advantage of the fact that the R
constant is the same even if the conditions of
the gas changes.
Change in Conditions Problem
51
A portable air tank holds 3 gallons of air at 90
psi. If you took it to the river to blow up 3
inner tubes each holding 6 gallons of air, what
pressure would they have?
90psi x 3gal P2 x 18gal
Start End
n1T1 n2T2
18gal 18gal
P1V1 P2V2 n1T1 n2T2
15 psi
52
Single condition problem

• 3 pounds (1,362 g) of dry ice (frozen CO2) is
  packed in a 1 gallon (3.785 L) glass jar. What
  will be the pressure in the jar after the dry ice
  turns to gas and warms to 20OC? (report pressure
  in psi and assume the jar doesn't explode)
• Change 1,362g to moles 1,362g x 1 mole 30.95
  moles
• 44.01 g
• Change 20OC to 293 K
• solve PVnRT for P P nRT P 30.95 moles x
  0.0821atmL/molK x 293K
• V
  3.785 Liters
• P 196.7 atm. Change to psi ? 196.7 atm x 14.7
  psi 2,891 psi
• 1 atm
• P 2,891 psi

53
O2
Kr
Gases are special in that no matter what the gas
is, the number of atoms (or molecules) in a set
volume is the same.
54
22.4 liters (5 gallons)
This much air weighs about 30 grams, or about the
same as 6 nickels.
55
Gas Density
56
22.4 liters (5 gallons)
The periodic table reports the atomic mass of all
elements. For elements that are gases, the mass
listed is what 22.4 liters (5 gal.) of that gas
would weigh at standard temperature and pressure
(0oC, 1 atm). Diatomic gases are double that
weight.
57
N2 O2 80 x 28 20 of 32 22.4 6.4
28.8 1 NH3 (ammonia) 14 3 17 17/28.8
0.6 the density of air. Cl2 35.5 35.5 71
71/28.8 2.49 times the density of
air. Gasoline C8H18 612 118 90 90/28.8
3 times heavier HCl (hydrogen chloride 1 35.5
36.5 36.5/28.8 1.27
58

• 520 gas cylinders (168 tons) of chlorine gas was
  first used as a chemical weapon at Ypres, France
  in 1915. 5,000 soldiers (about 1/3 American) died
  and 15,000 injured.
• The density of chlorine kept the gas close to the
  ground.

59

• Natural gas (methane) CH4
• Propane CH3CH2CH3
• Acetone CH3COCH3
• Carbon monoxide CO
• Hydrogen cyanide HCN
• Hydrogen sulfide H2S
• Carbon dioxide CO2

Using the Periodic Table calculate the density of
these compounds in the vapor phase. Assume
standard temperature and pressure.
60
In 1984 in a village in the African nation of
Cameroon.
Using the Periodic Table calculate the density of
these compounds in the vapor phase. Assume
standard temperature and pressure.
61
There is a lake known as Nyos. Its a beautiful
lake that fills the cauldron of a ancient
volcano. Nothing about it gives clues to the
danger that rests in its deep waters.
On the night of the apocalypse, Ephriam Che was
in his mud brick house on a cliff above Nyos.
Around 9 P.M., Che heard a rumbling that sounded
like a rockslide. Then a strange white mist rose
from the lake. He went to bed, feeling ill.
62
At first light, Che headed downhill. Nyos had
turned a dull red. He noticed the silence the
morning sounds of songbirds and insects were
absent. He also saw dead animals. Frightened, he
ran farther along the lake and downhill to the
village. There, nearly every one of the village's
1,000 residents was dead, including his parents,
siblings, aunts and uncles. It was the end of the
world, or so Che believed.
63
Eye witnesses said they saw an invisible river
coming down the hill knocking down brush and
small trees. It traveled at about 50 mph but
could not be seen.
All told, some 1,800 people perished around Lake
Nyos. Later the killer was found to be carbon
dioxide, which is not considered toxic, but its
high density keeps it close to the ground causing
asphyxiation. Density also caused it to flow
down the hillsides asphyxiating more people.
64
Scientists found the carbon dioxide had been
building up over time at the bottom layer of the
lake. Magma vents were pumping CO2 into the lake
forming carbonic acid (H2CO3) which essentially
is carbonated water. The water pressure kept it
from decomposing in to CO2 gas which would float
and dissipate. However, a rock slide or small
earthquake triggered the carbonic acid to
decompose into CO2 causing the lake to explode.
To prevent build up of CO2 scientists installed
pipes that reach down to the depths and trigger a
release of CO2. This huge fountain is only
powered by the release of CO2.
65
PVnRT
PV g RT
Molar mass
g RT
Molar mass
PV

• An automated early warning device could be
  designed to pump samples of air into a 4.0 liter
  container until the pressure was 3.0 atmospheres.
  At that point the container is weighed and the
  temperature taken. Lets say the net weight is
  21 grams and the temperature is 33OC (91OF).
  What molar mass would the device calculate?
• Molar mass 21g x 0.0821 atmL/molK x (27333)
  K
• 3.0 atm x 4.0 L
• Molar mass 44 g/mole, which indicates that the
  air is mostly CO2, so the alarm is sounded.

66
78 centimeters circumferenceC p x D78
3.1415 x D24.7 cm D12.35 cm rV 4/3 p r3
V 7937 cm3 8,000 cm3

• Molar mass gRT PV

Pressure 30 psiTemp 27oCMass of ball (empty)
600 gMass of ball filled 603 g
On a lighter note, lets solve an issue about
this little people basketball game. The
basketball seems too light. Calculate what kind
of gas the basketball is filled with.