Monthly Archives - December 2011

The Boyle, Charles and Cans

In the December CoolStuff newsletter, Bridgette Sparks of Saline High School in Michigan talks about using a discovery based lab exercise for the topic of pressure.
In my classroom I ask the students to calculate the net force on the can by giving them the dimensions of the can and an estimate of the reduced pressure in the can. For example if the pressure inside reduces to 8.0 PSI after the water vapor condenses a differential of 7 PSI produced the force that crushed the can. When the student multiplies this pressure difference by the number of square inches they have calculated the net force.

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Boyle, Charles and Cans… Oh, How I love the pressure!

You may have tried the can crushing pressure demo, you may have even tried it with a 55 gallon drum, but have you tried an entire tanker truck?   In the December CoolStuff Newsletter, Bridgette Sparks of Saline High School in Michigan talks about the high pressure environment she has created in her classroom!  Well, at least with the subject matter!

I, too, start my gas unit by having the class participate in a discovery based lab exercise very similar to the “Gas Laws Smorgasboard” mentioned in a previous Cool Stuff newsletter. Towards the end of class, I start playing David Bowie’s Under Pressure or Billy Joel’s Pressure since most of the lab stations are explained using pressure differences. When the students enter the classroom the next day we discuss pressure differences by observing the can crusher demo as a whole class. This time I use a larger paint thinner can and have the class explain using scientific principles. This is followed up with the next two questions and videos:

The air pressure is significant but could we do the same thing with a 50 gallon drum?

Or, how about a tanker car?

About Magdeburg hemispheres


The Magdeburg hemispheres are another cool example of how atmospheric pressure can have a significant effect on Earth. Invented by German scientist and mayor of Maddeburg, Otto Von Guericke in 1656 to demonstrate the concept of atmospheric pressure. By sealing a pair of large copper hemispheres with grease and the air pumped out, the sphere contained a vacuum and could not be pulled apart by a team of thirty horses until the valve was opened to release the vacuum.

The force holding the hemispheres together is equal to ~9000 lbs, equivalent to lifting a car.

Re-enactments of Von Guericke’s 1656 experiment are performed in locations around the world by the Otto von Guericke Society. The experiment has also been commemorated on two German stamps.

After learning about Guericke’s pump, Scientist Robert Boyle, working with Robert Hooke in designing and building an improved air pump. From this, they formulated what is called Boyle’s Law, which states that the volume of a body of an ideal gas is inversely proportional to its pressure.

A very big thank you to our contributors for this article:

Bridgette Sparks,
Chemistry Teacher
Saline High School
Saline, Michigan

Dwight “Buzz” Putnam,
Physics Teacher
Whitesboro High School
New York

Other Chemistry related products:

Pressure Globe

Vacuum Pumper Classroom Set

This affordable set of hand vacuum pumps and specially designed chambers that have a wide mouths let students test the effects of reduced pressure on many different objects, such as marshmallows. Classroom set includes 6 Vacuum Chambers and Pumpers, 6 Temperature Strips and teachers data sheet and student activity sheet.

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Atmospheric Mat

Cartesian Diver Kit

Air has weight, exerts pressure, and can be squeezed and compressed. The Cartesian Diver demonstrates all three properties using hands-on experiments. Make 30 plain divers with this kit.

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Atmospheric Mat

Gas Laws Demo w/ Temperature

Quantitatively confirm the Combined Gas Law with one complete apparatus! Students can verify this relationship using air and this unique apparatus.

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Original Gyro

Yenka Chemistry Software

The science simulation software platform from the makers of Crocodile Chemistry. Yenka gives you the tools you need in your classroom including both the Electro Chemistry and Inorganic Chemistry modules

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Vortex Rings in nature and your physics classroom!

You’ve probably seen a smoker blow smoke rings or you’ve created whirlpools in your tub or pool when you were little. These phenomena are known as Vortices, formed when a fluid swirls around a central point because of a complex combination of friction and pressure. These Vortex Rings are more common and widespread in nature than most people had probably thought; in fact, they are studied in great detail by aeronautical engineers and combustion scientists. But we just think they are cool! Take a look at the video and then read below as Physics Teacher Buzz Putnam of Whitesboro High School provides more commentary on these amazing natural occurrences:

The video illustrates Vortex Rings being formed by various sources including dolphins and volcanoes. You’ll notice in the video that the Vortex Rings are quite stable until they slow down and then at some critical speed, the core enlarges very suddenly causing the vortex to breakdown. Dolphins make, watch and chase them, even using their flippers to stop them rising in what appear to be games similar to those we humans play with soap bubbles. Watch Mt. Etna emit gigantic ring-shaped clouds of steam and gas up to 200 m in diameter that can fly up to 1000 m high, lasting more than 10 minutes. Your students will realize that humans aren’t the only ones who love to make and watch Vortex Rings, one of the coolest phenomena in nature!

Physics Teacher Magazine thinks it cool too!

The November 2011 cover for Physics Magazine shows the steam ring expelled by Etna’s summit crater.
View Physics Teacher Article>>

 

If you want to bring the vortex ring right into your classroom, you can do so with an Airzooka Air cannon and a fog machine (or fog in a can). Here is our Airzooka Air cannon in action:

Resources:

 

Do more with vortex rings right in your classroom, check out these great links:

BBC News article: Etna hoops it up

The Physics Teacher – Smoke Ring Physics vol. 49, November 2011.

Acknowledgements: Thank you to Dwight “Buzz” Putnam for his assistance in writing this Cool Stuff. Buzz is a 25-year veteran physics teacher at Whitesboro High School, New York Science Teacher of the Year and host of the Regents Physics Answers television show on PBS. You can also find him refereeing high school basketball games as well as presenting at the NSTA national conferences.

Products:

 

Air Cannon

Airzooka Air Cannon

This amazing new vortex launcher sends a strong blast of air all the way across the room!

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Super Fog Machine

Super FogA lab full of safe, non-toxic water-based fog in 2 minutes!
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Fog in a Can

Makes chemical fog quick and easy. Non-flammable and non-toxic. 8 oz. spray can.
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Air Powered Projectile

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Can a Helium Balloon Defy Physics?

Watch this video and it almost seems like this balloon’s actions are counter-intuitive to everything we know about motion and inertia. Let Professor Joel Bryan from Ball State University explain what is really going on.

 

 

Can’t see YouTube, try watching in Flickr.

Ask any student what happens when they are riding in a car and the car makes a sharp left turn, they’ll probably tell you that they, and everything else in the car that is not tightly secured, will be “thrown” to the right. Similarly, when the car turns sharply to the right, everything tends to be “thrown” to the left. They also probably know by experience that objects and passengers in the car keep moving forward when the car comes to a sudden stop – which is why seatbelts are required – and get “thrown” backward when the car suddenly accelerates forward. Science teachers frequently use these examples in discussions of Newton’s laws of motion, as well as addressing the widely held misconception that there is a “centrifugal” force that pushes the objects outward. If already in motion, the inertia of an object in the car tends to make it continue moving forward – regardless of how the car turns or changes speed. When accelerating the car from rest or some other constant speed, inertia tends to make an object in the car remain at rest or remain at its initial speed.


When students enter your classroom armed with these firsthand experiences, they may not at all be surprised by the video clips showing the direction an air-filled balloon hanging from the ceiling of a van swings when the car makes sharp turns to the left and right. However, they will likely be quite surprised to view the video clips of the motion of a helium-filled balloon inside a moving van as the van turns to the right and turns to the left.


The air–filled balloon hanging from the ceiling of the van behaved exactly as most would expect. The balloon swung to the left when the van turned right, swung right when the van turned left, swung backward when the van accelerated forward from rest, and swung forward when the van came slowed to an abrupt stop. This motion is easily explained using inertia and Newton’s first law of motion.


However, the helium-filled balloon that was attached to the floor of the van surprisingly moved opposite to the direction of the air-filled balloon. It swung to the right when the van turned to the right, swung to the left when the van turned left, swung forward when the van accelerated forward, and swung backward when the van accelerated backward (slowed abruptly to a stop).


One may initially think that this is a violation of Newton’s first law of motion, but the first law not only holds true, it is also useful in explaining the balloon’s behavior. When the van turned sharply to the left, air molecules inside the van continued moving forward and effectively were “thrown” to the right side of the van. This resulted in a greater density of air molecules on the right side of the van than on the left side of the van. The greater density of air molecules on the right side of the van created a buoyant force that pushed the lighter than air helium balloon from the greater density right side toward the lower density left side of the van. For similar reasons, the helium balloon swung to the right when the van turned sharply right. Once students understand this explanation, they should be able to predict and explain the movement of helium and air–filled balloons when the van speeds up and when it slows down.

See our cool tools for pressure and inertia

Inertia Apparatus

Inertia Apparatus

Do you know what will happen when the spring is released? Test students’ understanding of inertia and Newton’s First Law in a memorable way!
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Pressure Globe

Pressure Globe

Demonstrate the amazing power of air! This specialized bottle is fitted with a balloon and a stopper. Inflate the balloon with air or water, with the stopper in place and removed, and see what happens.

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Atmospheric Mat

Atmospheric Mat

Experiment with distance, time, velocity and acceleration, Newton’s laws and simple machines. The 120cm ramp attaches to the Workshop Stand at angles up to 65°.

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Original Gyro

Original Gyroscope

Even Sir Issac Newton would have been a fan of the Fan Cart! The Fan Cart is perfect for exploring Newton’s laws of motion, inertia, acceleration, and action-reaction.

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