Instead of high-tech rocket or electromagnetic forces, the jets are catapulted with the ancient power source of steam.

Helium atom is bouncing by using a custom motion path set to repeat until end of slide.

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.

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.

Centuries ago it was known that the pressure in a container could be increased dramatically by heating water in it.

The first engine was created using water in a heated container. An Egyptian named Hero invented it.

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 can’t. As the water molecules bounce around the chamber they strike all sides imparting a small push (pressure) on where it strikes.

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.

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.

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 don’t expect to follow it if you are new to PowerPoint animations.

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)..

Here’s are some pictures of the steam engines used in factories.

Here’s a portable steam engine that could be used around a farm.

The early steam locomotives were so novel that they charged people to see them work.

Some inventors wanted the engine to propel a vehicle that was both a boat and an automobile.

The steam locomotive was one of the most evident ways we put steam pressure to work.

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.

Gas: Alteration of Latin chaos space, chaos Date: 1779

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.

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.

the tallow dip to the electric light...

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

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 didn’t realize we would pack so many of these gas powered automobiles together. The pollution again returned.

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.

9

0

18

9 hits9 sec

1 hitsec

=

18 hits9 sec

2 hitssec

=

00010203040506070809

Seconds

½ volume Pressure comes from the gas molecules hitting the side of the container. Let’s 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.

Hits

So we saw that as volume decreases the pressure increases.

V=0.5 , P=2

V=0.1, P=10

V=6 , P=5

V=3, P=10

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.

9

0

18

9 hits9 sec

1 hitsec

=

00010203040506070809

Seconds

27 ºC = 300 K

27 ºC = 300 K

0 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

9

0

18

9 hits4.5 sec

2 hitssec

=

00010203040506070809

Seconds

27 ºC = 300 K

327 ºC = 600 K

327 ºC = 600 K

0 K

We are going from room temperature 27 ºC = 300 K to double that temperature, which is 600 Kelvin. Let’s 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.

15 psi, 300 K

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.

Another way to increase pressure is to increase the number of gas molecules. This is the approach the steam engine used by heating water.

Pressure is proportional to the number of gas molecules, which we count in moles.

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.

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…”

Let’s 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.

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.

As we also learned, we can increase pressure by introducing more molecules of the gas into the volume.

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.

1.4 x 1.4 = 2 doubles 2 x 2 = 2

1.5 x 1.33 = 2We 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.

• 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 atm•L/mol•K

• 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)

This is where I play an excerpt from the radio program “Car Talk.” In the recording the Car Talk experts mentioned PV=nRT when they were explaining why the pistons on someone’s hatchback wasn’t working in the winter.

This is where I play an excerpt from the radio program “Car Talk.” In the recording the Car Talk experts mentioned PV=nRT when they were explaining why the pistons on someone’s hatchback wasn’t working in the winter.

• Pressure=1 atmosphere• Volume=1 Liter• n = 1 mole• R=0.0821• What is the temperature?

Let’s 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.

Frozen carbon dioxide(Dry Ice)

Dry ice can achieve high pressure in the way water does when it turns into steam. However, dry ice doesn’t 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.

This is a copy of the water animation. I just changed the color of the liquid and spheres to white.

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 PV=nRT

Facts:2 Liter bottle

¼ lb = 454 g ÷ 4 = 114g

PV = nRT or P = nRT

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)

VCO2= 12g/mol + 2*16g/mol = 44 g/mol

114 g = mol44 g

2.61 mol

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)

2.6 mol x 0.0821 atm*L x 303 Kmol*K

P =2.0 L

n R T

V

P = 32.3 atmospheres

32.3 atm = psi1 atm

47514.7 psi

A heavy duty tire will explode around 75 psi, so we know this bottle is going to explode at 475 psi. Remember that’s 475 pounds every square inch. This bottle has about 50,000 lbs of total force pushing outwards.

• 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

CONVERSIONS

All Equal

Evangelista Torricelli

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.

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.

Manometersfrom Greek manos meaning sparse

sphygmomanometer• sphygmometer• Greek sphygmos meaning pulse (from sphyzein to

throb)

Measures to 300mm Hg

This is the inner mechanisms of certain pressure gauges.

When a pressure cooker is used, whatWhen a pressure cooker is used, what

causes the increased pressure?causes the increased pressure?

PV=nRTPV=nRT P=P=nRTnRT VV

Temperature goes from 25Temperature goes from 25ooC to 100C to 100ooCC

Turn to Kelvin by adding 273 to CelsiusTurn to Kelvin by adding 273 to Celsius

297K to 373K 75K/297K=25% increase in pressure297K to 373K 75K/297K=25% increase in pressure

Water vapor pressure

0.000

50.000

100.000

150.000

200.000

250.000

0 100 200 300

Temperature Celsius

PS

I

Series1

P1V1=n1RT1 P2V2=n2RT2

n1T1 n1T1 n2T2 n2T2

P1V1= R P2V2= R

n1T1 n2T2

P1V1= P2V2

n1T1 n2T2

Change in Conditions Problem

We can take advantage of the fact that the R constant is the same even if the conditions of the gas changes.

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?

P1V1= P2V2

n1T1 n2T2

Start End90psi x 3gal= P2 x 18gal

n1T1 n2T2 18gal 18gal

15 psi

Gases are special in that no matter what the gas is, the number of atoms (or molecules) in a set volume is the same.

O2Kr

This much air weighs about 30 grams, or about the same as 6 nickels.

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.

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 > 6*12 + 1*18 = 90 90/28.8 ~ 3 times heavier

HCl (hydrogen chloride= 1 +35.5 = 36.5 36.5/28.8 = 1.27

• 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.

• 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.

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.

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.

There is a lake known as Nyos. It’s 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.

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.

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.

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.

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. Let’s 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 atm•L/mol•K x (273+33) K

3.0 atm x 4.0 LMolar mass = 44 g/mole, which indicates that the air is mostly CO2, so the alarm is sounded.

PV= g RTMolar mass

PV=nRT

= g RTMolar mass

PV

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

Molar mass = gRT PVPressure= 30 psi

Temp 27oCMass of ball (empty): 600 gMass of ball filled: 603 g

On a lighter note, let’s solve an issue about this little people basketball game. The basketball seems too light. Calculate what kind of gas the basketball is filled with.