Vortex Tube

What it shows:

James Clerk Maxwell postulated that since heat involves the movement of molecules, it might be possible to separate hot and cold air in a device with the help of a "friendly demon" who would sort out and separate the fast and slow moving molecules of air. The vortex tube is such a device and does exactly that — using compressed air as a power source, it has no mechanical moving parts and produces hot air at one end and cold air at the other.

How it works:

Room temperature compressed air is supplied to the vortex tube...

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Paramagnetism of Oxygen

What It Shows

A large magnet with a small cylindrical gap allows a stream of liquid nitrogen to pass over and through. Poured liquid oxygen hangs between the poles in the strong field until it boils away.

How It Works

Pour the liquid nitrogen first, slowly over the pole pieces. The result is nothing but vapor condensation and crackling plexiglas; the liquid does not interact with the large magnetic field.

Next pour the liquid oxygen slowly over the pole pieces, and it collects in the gap between the poles. It might take two or three short pours to get the...

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Cloud in a Bottle

A 5-gallon bottle containing air and water vapor is slightly pressurized; a sudden release of the pressure cools the vapor, forming a cloud.

The bottle is a heavy Pyrex carboy with tooled mouth. A one-holed rubber stopper fits the mouth and is air-tight. A meter of Tygon tubing is fitted to a short tube in the rubber stopper.

The bottle is kept stopped and wet, and should work off the shelf. If the bottle is dry, spray about 10 ml of distillled water inside.

To demonstrate cloud formation, fit the stopper to the bottle and apply pressure with the lungs. Blow into the...

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Center of Mass

Irregular lamina with marked center-of-mass tossed in air.

What it shows:

The center of gravity fixed in (or outside) the object always orients itself with minimum potential energy on a vertical line below the support point. When an irregular shape is thrown into the air, it is seen to rotate about its marked center of gravity or center of mass (COM).

How it works:

We have several irregular lamina to suspend and/or throw in the air. They are (1) an amoeba shaped piece of masonite pegboard, (2) a cut-out map of the U.S. glued...

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Special Bouncing Collisions

Same as previous except that mass ratio of balls is 1:3 (softball:basketball) leaving basketball dead and softball four times the height.

tennis and basketball

Molecular Size

Also known as the Ben Franklin pond experiment, after a story in B.F's autobiography.

Olive oil with a known volume is dropped onto water. The water has been dusted with lycopodium powder, which floats on the surface. The oil drop expands, pushing the powder aside to form a clear circle, until the oil forms a monolayer. Measuring the area of the monolayer, dividing the volume of the drop by that area, gives the thickness of the monolayer, which is the height of the oil molecule on water.

From our demonstration movie, we found these values. The size of the patch was 62 cm...

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Solid, Liquid, Gaseous CO2

Observation of phase changes with corresponding pressure changes.

A two ml. plastic microcentrifuge vial and a small shop vise are used together to melt dry ice.

Wear safety glasses for this demo. The vial can explode, or shoot out of the vice, from the pressure of liquid carbon dioxide. Set up a camera with a close shot of an empty vial before putting in a loaded vial.

Crush a pellet of dry ice to make pieces that fit into the vial. Place a couple of pieces in the vial, and snap the lid closed.

Immediately place the vial horizontally in the jaws of the vice,...

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