Reaction of Propane and Oxygen

An oxy-propane torch is lit with just propane, and the flame examined, before oxygen is added, changing the flame character and temperature.

The torch head is gaffed to the table top with enough slack to turn the gas valves. The propane tank and the oxygen tank are on separate dollies. The torch valves are closed, and the tank regulators set so there is about three pounds of pressure behind each gas. (The precise settings of the regulator are a good thing to check out in a practice session before doing this demo.)

With a friction lighter in one hand, open the propane valve on...

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Reaction of Sodium and Water

Sodium undergoes a reaction with water.

A liter of warm water in large pyrex vessel, covered with fine mesh stainless steel screen, is on a stool close by in-floor vent hood.  Add a few drops from the phenolphthalein indicator bottle.

Using the long forceps, pick out a pea size lump of sodium metal from the mineral oil in the small beaker. Wipe off the lump on the dry paper towels. With the vent fan running, lift the edge of the screen and drop in the sodium metal. Replace the screen and get back.

The sodium will from a hissing ball of molten metal, which bounces...

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Reaction of Hydrogen and Oxygen

Blue balloon with hydrogen, green balloon with helium, red balloon in back with hydrogen and oxygen mixture, and, on a cart, a red water balloon on large watch glass. Candle on a stick with matches, and a needle in the end to prick the water balloon.

Safety glasses and hearing protection is required for the demonstrator and anyone else who can't cover their ears for the red balloon.

Reactions of Li, Na, and K with Water

Lithium, sodium, and potassium undergo reactions with water.

Two liters of warm water in large pyrex vessel, covered with fine mesh stainless steel screen, is on a stool close by in-floor vent hood.  Add a few drops from the phenolphthalein indicator bottle, and a few drops of 1M hydrochloric acid if the warm tap water turns pinkish.

Video camera is clamped to the stool leg, and pointed at the bottom of the beaker. Before class, frame the shot and focus on the center of the beaker.

Using the long forceps, pick out the coil of lithium wire from the mineral oil in...

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Hot and Cold Gas in Balloons

A balloon is dropped in boiling water, and another balloon is cooled with liquid nitrogen to demonstrate the effect of temperature on volume of gas in a balloon.

A 4 liter beaker on a hot plate, with a liter of water boiling within. A prepared balloon, filled with air and tied so that it just fits in the beaker, is dropped into the beaker. The balloon expands to seal the beaker and is forced up by the vapor pressure, ending up on top of the beaker, too large to fit inside.

A foam ice bucket will hold a helium ballon that is large enough to seal around the inside of the bucket...

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Greenhouse Bottles

Simulation of the greenhouse effect with silvered and unsilvered glass bottles.

What it shows:

Heat energy readily escapes from a clear glass flask, but is trapped inside a silvered flask which rapidly heats up.

How it works:

Two 2L flat bottom Florence flasks, one clear and one silvered (see reference), have identical 10Ω, 25W resistors placed inside them connected in series to a DC supply 1 These resistors act as good sources of infrared radiation. The clear flask readily transmits the IR, but the silvered...

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Smog in a Bottle

Nitrogen dioxide is produced by an electric discharge in air and, when sprayed with a water mist, produces acid rain.

What it shows:

Some of the most irritating and dangerous pollutants in our atmosphere are gases such as sulfur dioxide and nitrogen dioxide. Nitrogen dioxide is a deep orange-red gas that, together with smokelike particles, is responsible for the color of smog. In this demonstration, nitrogen dioxide is produced by an electric discharge in air and, when sprayed with a water mist, produces acid rain.

How it works:...

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Coriolis Effect

As demonstrated by two people throwing a volleyball to each other while sitting on rotating platform.

What it shows: 

The Coriolis force is a pseudo force existing in a frame that rotates with constant angular velocity to a reference frame. It acts on a body moving in the rotating frame to deflect its motion sideways. Here the audience sits in the reference frame, while two volunteers on a rotating platform experience the coriolis force by trying to basket a volleyball.


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Local Group of Galaxies

Lights-up-in-the-dark three-dimensional model of the local group.

What it shows:

Three dimensional model of the local group of galaxies, with a scale of 1mm = 1kpc.

How it works:

A large wooden base board forms an x-y plane from which the approximate relative positions of the local galaxies are measured. The galaxies are LEDs and (for the two biggest, the Milky Way and Andromeda) 6V bulbs, mounted atop 8mm diameter plastic tubing; the length of the tube gives a z-axis position of the galaxy. The wires from the LEDs and...

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Binary Star

Two small closely mounted bulbs simulate resolution problems.

What it shows:

The ability to resolve two closely separated stars depends upon the aperture size of the observing instrument. Here two tiny bulbs represent stars that are barely resolvable by human eyes across the lecture hall.

How it works:

The light collected from two stars by the eye (or by a telescope mirror) are themselves geometric point sources but are circular diffraction fringes

The light from a distant star is not detected as a geometric point...

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Kepler's Machine

Working model to show Kepler's 1st and 2nd laws and the equivalence of the area law to the law of equants.

What it shows:

A demonstration illustrating the equivalence of Kepler's second law, the Law of Areas, with the Law of Angles.

How it works:

In order to determine the orbit of Mars using circular orbits, Kepler had to offset the focus of Mars' orbit from the Sun to a point C (figure 1). Kepler's 2nd Law of planetary motion states that a planet's orbit around the Sun will sweep out equal areas in equal times....

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Static model of site; can be used with light source to simulate a mid-summer's morning.

What it shows:

1:50 scale model of the Stonehenge site with the positions of Sun and Moon on important dates marked. It can be used with a light show to reproduce Sunrise on Midsummer's morning, June 21.

How it works:

The Stonehenge site consists of the sarsen circle of 30 megaliths capped with 30 lintels. Within this circle is a horseshoe pattern of five trilithons. 80m north-east of the circle's center is the Heel Stone; it is the...

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Equatorial Ring

Model of Ptolemy's ring used to measure the length of the year.

What it shows:

This is a model of the ring and method used by Claudius Ptolemy (2nd century A.D., Alexandrian astronomer) to determine the length of a year.


How it works:

The ring is...

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Sodium Absorption

What it shows:

Sodium 'D' line absorption showing up as a black line in the yellow of a continuous spectrum. Good as a simulation of the sodium portion of the Fraunhoffer absorption spectrum caused by atoms in the solar atmosphere; it does not however, resolve the 5890/5896Å doublet.

How it works:

As in the Sun, which is a black body source surrounded by an atmosphere of cooler gas containing many heavy atoms including sodium, we can set up a black body spectrum using a slide projector, and provide a hot sodium 'atmosphere' using...

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What it shows:

A superconducting material in the presence of a magnetic field excludes that field from its interior. This is shown by levitating a magnet above a high temperature superconductor.

How it works:

We have a 25mm disc of ceramic yttrium barium copper oxide YBa2Cu3O7 that becomes superconducting above liquid nitrogen temperatures (Tc = 90K). Using a cubic neodymium magnet 4mm of side, two effects can be shown. Firstly, the Meissner effect itself, by placing the magnet on the...

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