A brownie pan with two food safe thermocouples, one in the brownie batter and one in the air next to the pan, is put in a pre-heated oven, and the temperature profiles recorded and displayed.
Clean copper wire is used to make an armature for the thermcouple wires. Crimp the center of a 20 cm piece of 14 ga wire on the side of the baking pan. Bend loops at the ends of the copper wire to hold the thermocouple wire.
The oven temperature thermocouple should be about five centimeters away from the pan, at the same level as the center of the pan. The brownie thermocouple is...
A volunteer puts her hands in oil and water in large beakers on thermostated hot plates, at about 60°C. The water beaker hand is removed almost instantly. The oil beaker hand can remain indefinitely.
The heat capacity of oil is about half that of water. Oil is thought of as hotter because it can be heated to higher temperatures than boiling water, but at the same temperature, water moves more heat into your hand than oil does.
A big insulated bowl is filled with liquid nitrogen and marshmallows, which when frozen, are eaten in spectacular fashion.
Regular size marshmallows. Use wooden spoons, big bowl with holes for draining. Push down the marshmallows in the liquid nitrogen and mix to evenly freeze. Serve to volunteers.
Eaten with open mouth and exhaling slightly gives the effect of dragon's breath.
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...
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...
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.
Total internal refraction of laser beam through sugar solution with refractive index gradient; representative of seismic waves through Earth's mantle.
What it shows:
As a simulation of atmospheric refraction, this demonstration shows the gradual and continuous bending of light due to a gradient in the optical density of the medium. In this case the variable refracting medium is a tank of sugar water with a vertical gradient in the concentration of sugar and a HeNe laser provides the light beam. It can be used as a model of mirage formation (except that the...
As shown in the drawing, the Mercator projection is a cylindrical map projection of the spherical globe. The meridians and parallels of latitude on the globe end up appearing as lines crossing at right angles in the projection. Areas on the globe far from the equator appear to be much larger on the projection. It's not trivial to visualize this projection and the intention of this demonstration is to shed some light on it (literally).
The aberration of starlight is the shift in the position of the image of a star due to the rotation of the Earth about the Sun, and is a consequence of the finite velocity of light. For a star directly overhead, a telescope will have to be angled by v/c to the vertical where v = velocity of the Earth in space, in order that the telescope be pointing at the star. The equipment necessary to show aberration is one umbrella.
Handy size model of a generic spiral galaxy to show salient features or to describe structure of the Milky Way
How it works:
The model is a 30cm diameter Plexiglass disc 1cm in thickness, with a Ping-pong ball stuck through the center to represent the nucleus. The spiral arms of the galaxy are sprayed on with white paint, and we've stuck on a "you are here" arrow pointing to the outer reaches of one of the spiral arms at the approximate position of the Sun in the...
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...
Static 3-D model showing the orbital paths of Jupiter's satellites.
How it works:
The model marks the orbital paths of the Jovian satellites to a scale of 1.5cm = 106 km. This scale allows the orbit of the outermost satellite Sinope to fit within a 1m × 1m plywood base. The orbits of the outer 8 satellites are marked using loops of 2mm × 1mm spring steel supported to their correct heights by 5mm Plexiglas rods (Pasiphae rising to the greatest height of 42cm). The...
Spinning frame that demonstrates equatorial bulge (oblateness).
What it shows:
The rotation of a planet about its axis causes its equator to bulge due to the "centrifugal force" acting on its mass. Here a spinning wire frame simulates the effect.
How it works:
Planets are actually oblate spheroids rather than spheres due to their rotation. This device consists of two spring metal rings mounted on a metal axis. The north pole is free to slide so that, as the frame spins, the hoops flatten and the equator bulges. The axis is...