Transcript Gas Laws & Fluid Principals PowerPoint Notes

•
•
•
•
•
Students should definitely do yoyo lab with microwaving ivory soap!
ADD MATH TO MATH LAWS! AT LEAST SHOW EQUATIONS, EVEN IF YOU DON’T
DO THEM
LOOK AT THE STUFF BRYAN GAVE ME. HE DOES MORE MATH WITH GAS LAWS.
Put eyes on the Pascal's principle demonstrator …tube is like smile
Archimedes & Bernoulli need mascots! Bernoulli – straw, Archimedes – Archimedes!
•
Inquiry intro!!
– Do the computer simulation in the computer lab to intro this chapter.
•
Review all three laws, maybe do front of that sheet, after we finish the three
laws.
–
•
Then do the back after doing principles.
–
•
•
•
•
Give a quiz after gas laws! Very short multiple choice. Students check it
Give a quiz after principles! Very short multiple choice. Students check it
MUST GIVE STUDENTS QUESTIONS EARLIER ABOUT WHICH LAW IS
THIS AND EXPLAIN HOW! EXPLAIN AN EXAMPLE FOR BLAH’S LAW.
Egg in bottle – can do with plastic bottle I think, could do with plastic bottle by
squeezing, putting egg on, then releasing (boyle), could do in bell jar too, is
neat to do same trick via several laws!
Cartesian diver – increase pressure, decrease volume?
Then do lab
– Give homework on the math problems (Pascal)!
– Review Lab
– Study Guide
Bell Work 11/6 – 4 min
Start a new bell work sheet titled “Gas Laws”.
1.If you heat a gas, what happens to it’s
volume?
2.Define pressure in your own words.
3.Do you know anyone named Charles?
Anyone at all?
Today you are going to…take notes & see cool demos &
videos on Charles’ Law and Gay-Lusaac’s Law.
So you can…develop an understanding and ability to
predict gases behavior. That way you won’t kill
yourself and you’ll improve your gas mileage!
You’ll know you’ve got it when…you can
• State both laws and identify their differences and
similarities
Gas Laws & Fluid Principals
Mask!
REVIEW
• Volume
• Temperature
• Pressure
Pressure
• Pressure – is the amount of force
exerted per a given area.
• Pressure = force/area
– Force - push or pull
• Less area, more pressure
– Book flat & sideways
– Knife
– pressure points
Pressure
• bed of nails (5 min max!)
• Same force spread over large area, force
per nail = 150 lbs/400 nails
– Balloon too!
Directly & Inversely Proportional
• Directly proportional – increasing or
decreasing together with a constant ratio
• Inversely proportional – increasing or
decreasing opposite one another with a
constant ratio
– Pressure
– Density Equation
Charles’ Law
• “If pressure is kept constant, the volume
of a gas is directly proportional to its
temperature.”
– Happens in flexible containers
– If temp. increases, volume increases
– If temp. decreases, volume decreases
Applications of this law:
• Hot air balloon
– Heat air up & it expands. Balloon gets less dense
• Balloon in hot water!
• As air cools in winter, it’s volume decreases
– Add air to car tires. (In summer, you may need to…)
– Don’t leave inflated sports balls outside in the
winter.
• Backdraft! https://www.youtube.com/watch?v=RLUhwGLJhsI
– Oxygen reintroduced to burning room, fire burns more & added heat
causes the fiery air to expand
Charles’ Law continued.
• www.youtube.com/watch?v=IkRIKGN3i0k
• Helium balloon in liquid nitrogen
– Temp changes from 25oC to -196oC
– Volume is 1 L
– How much is new volume?
Pressure of a Gas
• What is pressure again?
• Pressure of a gas is caused by all the gas
molecules bumping into a surface
– Air molecules move over 100 mph!
– Each air molecule collides with one or another of its
neighbors 10,000,000,000 times per second!!!!
– The more often they bump a surface, the more pressure
• Still a force over an area
• Look at cool simulation!!
• Vacuum pump
Atmospheric Pressure
• 14.7 lbs/in2 at sea level
– The weight of all air above compresses air
below, raising air pressure near sea level
• Things move from HIGH to LOW pressure!
• Demos?
–
–
–
–
–
–
Suction cup
Stick two discs together
License on jar
Straw holds water
Holey bottle (BL)
Human Vacuumed
into garbage bag
Atmospheric Pressure
• Things don’t suck, they blow.
• Drinking Straw
Reverse Drinking Straw
Gay-Lussac’s Law
• demo…inquiry learn
– Maybe a different demo instead?
– Could look at the gas simulation…
Gay-Lussac’s Law
• If volume is kept constant, the pressure of a
gas is directly proportional to its temperature.
– increasing the temperature increases pressure
– decreasing the temperature decreases pressure
• Applies to rigid containers of gas (The
volume can’t change if container is rigid.)
Gay Lusaac’s Law
• Gay Lusaac’s pressure gauge demo
• As gas in sphere is heated, pressure
increases
• BLEVE
• As bleve gets hotter, pressure builds until
bleve explodes
CAN DEMO
• Can with water heated then inverted
• As can is heated, temperature of the gas inside
(increased/decreased), so volume (increased/decreased).
Who’s law is this?
• Faster moving particles result in more collisions, which would
increase the pressure if the can were sealed – instead, the air
expands and particles leave out of the opening of the can.
• The pressure is kept the same because less, faster moving,
particles are needed to get the same number of collisions as
before.
• Can is flipped into cold water, temperature of the gas inside
_____________, so the pressure of the gas inside
_________________. (__________ law)
• Particles slow down, reducing the number of collisions,
reducing the pressure. The outside pressure is now greater ,
and it crushes the can.
CAN DEMO
• When gas inside can is cooled, pressure
inside decreases, causing can to be
crushed by greater air pressure outside
Cool Videos
• Barrel
• http://www.youtube.com/watch?v=n3cu_Q119s
• Other thing train
• http://www.youtube.com/watch?v=Zz95_V
vTxZM
Gay Lusaac’s Law applications
• All of these have this in common: temperature
increases, causing gas pressure to increase until it
explodes.
• Never store fire extinguisher close to stove
• Never store propane tank near furnace
– Just to be safe, don’t store it inside house.
• Never throw a spray can in a fire. Heating closed
containers in microwave
– Always hold heated containers away from face when opening!
• Cannons & bullets
– Extreme heat creates enough pressure to launch
projectile
Gay Lusaac’s Law applications
• CO2 cartridge (or can) releasing air
Closure
• Explain the difference between Charles Law
and Gay Lussac’s Law
Bell Work 11/7/13
• Define Charles Law and Gay Lusaac’s Law and
give 1 demo/application of each.
Today you are going to…take notes & see cool demos &
videos on Boyles’ Law, pressure, and Pascal’s
Principle.
So you can…develop an ability to predict the behavior of
gases and fluids.
You’ll know you’ve got it when…you can
• State Boyles’ Law and Pascal’s Principle and list some
applications for them.
• Explain the relationship between force, area, and
pressure.
Nurse Boyle!
Boyle’s Law
• If temperature is kept constant, the volume of a
gas is inversely proportional to its pressure.
– Increasing volume of gas decreases gas pressure
– Decreasing volume of gas increases gas pressure
Boyle’s Law
• Increase volume of syringe, gas pressure decreases.
• Decrease volume of syringe, gas pressure increases.
Boyle’s Law Applications/Demos
• If you squeeze a balloon too hard, the pressure will increase
and it will POP!
• If a tractor trailer truck receives a heavy load, the driver should
remove some air from the tires. Why?
– Added weight causes tire volume to decrease, so air pressure increases
• Turkey baster
– as you release the bulb, volume increases and gas pressure decreases.
Fluid gets pushed inside.
• Balloon in a syringe – volume increases, balloon inside
expands as pressure decreases
• Bell Jar Demos
•
balloon, shaving cream, marshmallows, water in jar, water bottle, heated water,
Boyle’s Law Applications/Demos
Lungs
http://www.youtube.com/watch?NR=1&v=msphJo
HIqiU&feature=endscreen
Muscles move chest out.
volume increases, pressure decreases, air is pushed in
Muscles contract chest
volume decreases, pressure increases, pushing air out
Who’s Law?
Can of Air
• Which law?
– What do we notice?
• As air leaves the can, pressure inside the
can ____________, so temperature inside
the can ______________.
Bell Work 11/8/13
1. Complete the following chart by filling in
“constant”, “directly” or “inversely”.
Law
Boyle’s Law
Gay-Lussacs’
Law
Charles’ Law
Pressure
Volume
Temperature
• http://www.youtube.com/watch?v=yVTN8B
Ge4-s
Pascal’s Principle
• Pascal’s Principle- pressure applied at one
point of an enclosed fluid is transmitted equally
in all directions.
– Pass around demonstrator!
– That’s why bubbles are spherical!
Applications of Pascal’s Principle
• Pascal’s principal can be used to:
1. Transmit a force
• Toothpaste – squeeze on sides, pressure is transmitted
everywhere, so it comes out the opening
• Car brakes – pushing pedal pushes on break fluid,
pressure is transmitted to brakes
• Water guns (both Boyles’ Law & Pascal’s Principal) –
pressure applied at trigger is transmitted everywhere;
water comes out opening
Pascal’s continued..
• Pascal demonstrator – students will examine and
explore.
– Observations?
Pascal’s Principle
• Hydraulics- lifting objects by squeezing a
fluid in an enclosed system.
– since pressure is equal everywhere, when the
pressure of the fluid is transmitted to a larger
area, the force is multiplied.
• Since gases compress, liquids work better
– You gain force, but you lose _______.
•
http://www.youtube.com/watch?v=A3ormYVZMXE&feature=related
Applications of Pascal’s Principle
• Pascal’s principal can be used to:
2. Multiply a force
• Hydraulic jacks – pressure applied on
small area creates increase force on large area
• Brakes - pressure applied on
small area creates increase force on large area
Applications of Pascal’s Principle
• Pascal’s principal can be used to:
2. Multiply a force
• Heavy machinery/equipment
Bell Work 11/11/13
1. If an metal has an mass of 200.0 kg and an volume
of 50.0 m3, what is it’s density?
2. If you had 18.0 m3 of the same metal, what would its
mass be?
Units of Pressure
• Pounds per square inch (psi or lb/in2) (America!)
• Pascal (Pa) – unit of pressure
• 1 Pa = 1 N/m2
1.0000 Pa = 0.000145 psi (that’s reeeaaaly small!!)
1.0000 kPa = 0.145 psi
1 atmosphere = 14.7 psi = 101.3 kPa
According to Mr. Shuster, your feet feel a pressure of 1-5
psi when flatfooted
Pascal Problem One
Explain subscripts!!!
Make triangle!!!
A1 = 10 in2
A2= 1,000 in2
F1 = 15 lb
F2 = ?
P = ? psi
Compare to density!
Pascal Problem Two
A1 = 8.0 in2
A2= 1440 in2
F1 = 30.0 lb
F2 = ?
P = ? psi
Pascal Problem Three!
A1 = 8.0 m2
F1 = 50.0 N
P=?
A2= 24 m2
F2 = ?
Pascal Problem Four
A1 = 2.00 m2
A2= 80.0 m2
F1 = 3000.0 N
F2 = ?
P = ? psi
A1 = 10 cm2 F1 = 50 N
A2= 35 cm2 F2 = ?
P=?
A1 = 10 cm2 F1 = 50 N
A2= 35 cm2 F2 = ?
P=?
A1 = 7 cm2
F1 = 155 N
A2= 98 cm2 F2 = ?
P=?
Bell Work 11/12/13 – 4 min
A1 = 7.0 cm2 A2 = 98 cm2
F1= 155 N
F2 = ?
P=?
Bernoulli’s Principle
• Demo 1st
– Inquiry learning!
– Blow over paper
– Blow under paper
– Blow between papers
Bernoulli’s Principle
• “As the velocity of a fluid increases, the
pressure exerted by the fluid decreases.”
– Objects always move from areas of high
pressure to areas of low pressure.
– http://www.youtube.com/watch?v=sQnCD7p3
CrU&feature=related (The 2nd best video ever made.)
Examples of Bernoulli’s Principle.
• Blow across the top of a paper, What do you think will
happen? What actually happens?
• Pressure of moving air above paper is less, paper is
pushed upwards
• Take two sheets of paper and blow between them. What
do you think will happen? What actually happens?
• Pressure of moving air between paper is lowered,
papers move together
Examples of Bernoulli’s Principle.
• Ping pong ball in funnel
• Pressure of moving air in funnel is lowered, ball is
pushed into funnel
• Blow across top of straw
• Pressure of moving air over straw is lowered, water is
pushed up straw
Examples of Bernoulli’s Principle.
• Pipe n Styrofoam ball
• Moving air near bottom of ball has less pressure, ball is
pushed towards moving air
• Trains & boats passing, Truck passing car
• Moving fluid between vehicles has less pressure,
vehicles are pushed together
Examples of Bernoulli’s Principle.
• Julius Sumner Miller
• This site shows the effect of smaller area has on the
speed of the particles.
• textbook demo
– 2 POP CANS (no, tomorrow )
– Ping pong ball (no, tomorrow )
QUESTION!
• Objects move from areas of high pressure
to lower
• How does the shape of an airplane’s wing
enable it to fly?
Applications of Bernoulli’s Principle.
• Bernoulli’s principle explains why airplanes fly.
• The wing of an airplane is curved so that the air
goes faster over the top of the wing. This
reduces the air pressure on top of the wing.
The greater air pressure below lifts the airplane
up.
• This site contains a 10 minute video illustrating
Bernoulli's Principle as it relates to flight
Applications of Bernoulli’s Principle.
• Curveball
• Frisbee
• Boomerang
Archimedes
• Archimedes invented the water screw, the
claw, simple machines, mirrors and lenses.
(Students are not responsible for this info.)
Archimedes’ Principle
• Buoyant force – force of liquid pushing
something up
• Holds you up when you’re swimming
• Makes things underwater lighter!
Archimedes’ Principle
• “The buoyant force on an object in a fluid is
equal to the weight of the fluid that the object
displaces.”
• Buoyant force = weight of displaced fluid
• Demo of Archimedes’ Principal by Bearded Professor (One of
Shuster’s many uncles)
– http://www.youtube.com/watch?v=g6aErhwFXsg&f
eature=related
Archimedes's Principle
• As an object sinks into the fluid, there is more
fluid displaced by the object, increasing the
upward buoyant force acting on the fluid.
• Demo?
• Video demo! (Kid in orange shirt)
If the object has a weight of 12 lbs, how
many lbs of water was displaced?
? Lb
Water
1. One cubic foot of seawater weighs about 64 lbs.
Suppose you pour one cubic foot of seawater into a
massless plastic baggie, tie the baggie closed with
no air bubbles inside, attach a string to it and lower it
into the ocean. When the baggie of water is
completely submerged, how much force do you have
to exert on the string to hold it up?
A. 0 lb
B. 24 lb C. 64 lb D. 128 lb
E. you have to push it down because it tends
to come up
How much does the object really weigh?
What is the buoyant force?
How much does the object really weigh?
What is the buoyant force?
If the object has a weight of 12 lbs & weighs 9 lbs
in water, how many lbs of water was displaced?
Archimedes Principle
• So, Why do some objects float in water?
• Objects that are more dense than water ______
•
Objects that are less dense than water___________
• If something is floating, it is displacing exactly it’s
weight in water!
– object floats if buoyant force = weight of object
• Buoyancy - ability for things to float.
Archimedes Principle
• Why can a heavy ship float?
How much water does a 2 ton boat displace?
• So how was this principle discovered?
– http://www.youtube.com/watch?v=ZUYkBeAW5hc&feature=related
Archimedes Principle
• If a 50 lb kid gets onto a boat, how much will it
sink? (Enough to dis…)
– Aluminum boat in sulfur hexafluoride
• Water has a “weight density” of 8.34 lb/gallon.
How many gallons of water would a 150 lb
person displace?
• Mercury has a “weight density” of 113 lb/gallon.
How many gallons of mercury would a 150 lb
person displace?
– Use different fluids, like mercury, air, sodium hexafluoride
– Do example – something in alcohol & something in salt water!
• Egg?
– Drop graduated cylinder in water!
Who is this?
Who is this?
END
Hydrometer
• Use to measure density of liquids directly
•
•
Used in fish tanks & wine making
http://www.ehow.com/video_5226052_use-hydrometer-fish-tanks.html
Bell Work 10/30/12
1.
2.
3.
4.
5.
6.
Pressure and volume are inversely related.
Volume and temperature are directly related.
Pressure and temperature are directly related.
Moving fluids have less pressure.
Buoyant force = weight of water displaced
Pressure in an enclosed fluid is transferred
without changing
7. When we change the pressure, volume, or
temperature of a gas, does it’s mass change?
Do the number of particles change?
Bell Work 11/1/12
1. What causes pressure exerted by gas molecules?
(What are the molecules doing?)
2. When scientists record the volume of a gas, why do
they also record the temperature and pressure.
3. As the temperature of a gas increases, what happens
to particle speed? What happens to volume if it is in
a flexible container? What happens if it’s in a rigid
container and volume can’t increase?
Bell Work 11/2/12
1. A closed water bottle (with just air in it) is put into the
freezer. What will happen , why, and what law is
this?
2. 10 years from now it’s Thanksgiving day and Victoria
Fox is cooking turkey for the fam. Suddenly the fire
extinguisher above the stove explodes! Why, and
what law is this?
• Matt throws a 20.0 lb rock into the water.
If it displaces 12.0 lbs of water, how much
will the rock weigh underwater?
• Who’s principle?
• Egg on bottle
– As the paper in the bottle burns, the gases inside
the bottle are heated.
– The volume of the air in the bottle increases, the
bottle increases with temperature, causing some of
the gases to be forced out past the egg. This is
______________’s law
– When the flame burns out, the temperature
decreases, causing pressure inside the bottle to
decrease.
– This is ______________’s law
– There is _________ pressure on the outside of the flask
pushes the egg into the bottle (lower pressure).
Egg on bottle
• As the paper in the bottle burns, the air inside the
bottle is heated, causing the volume of the air to
______________. This is ______________’s law
• Some of the gases are forced out past the egg,
therefore some air has left the bottle.
• When the flame burns out, the temperature
______________, causing pressure inside the bottle
to ______________.
• This is ______________’s law
• There is _________ pressure on the outside of the
flask pushes the egg into the bottle (_________
pressure).
Bottom of Bottle Example
http://www.youtube.com/watch?v=epOwdGI
DzlY&feature=related
Bell Ringer 10/20 – 3 min
1. What principle is being applied to lift the
car?
Pascal Problem One
A1 = 10 cm2
A2= 60 cm2
F1 = 50
F2 = ?
Pascal Problem Two
A1 = 15 cm2
A2= 85 cm2
F1 = 200 N
F2 = ?
Bell Ringer 10/21/11
A1 = 13 cm2 F1 = 70 N
A2= 39 cm2 F2 = ?
P=?
Check Homework!
Archimedes's Principle
Upward buoyant force = weight of the fluid displaced by the
object.
Change in weight = weight of the fluid displaced by the object.
Bell Ringer 10/26
1. Use Archimedes’ Principal to determine
how many lbs the object weighs out of
water. (bottom right)
2. One penny has a weight of 0.0274 N.
What was the buoyant force on your boat
just before it sunk?
2 Lb
Water
How much does this object
weigh?
• What’s the magnitude of buoyant
force?
5 Lb Water
If the object has a weight of 12 lbs, how
many lbs of water was displaced?
? Lb
Water