Exploratorium EXNET Rental Group 2

Training at Toledo May 2003

Here are Snacks and lessons which complement the exhibits in rental group 2.

Paul Doherty

Blue Sky

The sky is not blue because air molecules absorb yellow light as the indigo pigment in blue jeans does. It is blue because air molecules scatter blue light to the side more strongly than they scatter red light.

Blue Sky Hot Melt Glue, a Snack to accompany this exhibit.

Glue Stick Sunset Snack

Phase Pendulum: Hands on exploration of why the sky is blue.

Why is the sky blue?: Essay

Bridge Light

Newton saw the phenomena known as Newton's rings which you can see at this exhibit. Newton's rings show that light behaves like a wave, yet even though he saw the rings, Newton stuck to his belief that light was a particle. Sometimes seeing is not believing.

Bridge Light Snack, interference patterns can be seen between two clean microscope slides.

Chaotic Pendulum

You can create your own Snack of this exhibit by buying a toy known as "Pendulum Man."

Chaotic Pendulum Exploration, discover the essence of chaos.

Colored Shadows Exploration: Use the Colored Shadows exhibit to explore color subtraction.

Diffraction

Diffraction Snack, a minimag light provides a great point source for exploring diffraction of light.

Light Island

Light Box Snack, how to build a simple lightbox and use it to find images.

Molecular Buffeting Model

Modeling solids, liquids and gasses

Feynman's statement of the most important thing science has learned: "All ordinary matter is made of atoms, small indivisible particles which attract each other when a little ways apart and repel each other when close."

When the motion of the balls in this exhibit is reduced they all gather together and gently vibrate, they seldom change places. The balls form a model of a solid. If the balls perfectly interlock in an orderly array, they model a crystalline solid.

Increase the motion of the balls so that they are mostly touching each other but move around, changing places often. They model a liquid.

Increase the motion to the max and the balls zip around through the entire exhibit rarely colliding with each other. They model a gas.

The definition of temperature circa 1900.

In a gas the temperature is defined as the "average random kinetic energy of translational motion per molecule." When the balls move at a high speed, this exhibit models a high temperature gas.

Molecular Buffeting Snack: a rat cage full of Styrofoam balls or ping pong balls can be shaken to model solids, liquids or gasses.

An alternative snack can be made by giving a classroom full of students one balloon apiece. If the students wave the balloons the model a solid, if they exchange them they model a liquid, and if the throw them around they model a gas.

Resonant Pendulum

Galileo discovered that the period of a pendulum's swing is independent of its amplitude. We now know that the period is independent of the mass of the pendulum. The period depends upon its length.

If the pendulum swings in a circle the period of its circular motion is the same as the period of its back and forth motion. A circular motion is the combination of two back and forth motions at right angles to each other.

Resonant Pendulum Snack: A steel paint bucket full of sand is used to create a pendulum which is driven by magnets on strings.

Resonant Rings

Resonant Rings Snack

Resonator

Resonator Snack: Model the behavior of buildings in an earthquake, and the color-detecting cones in the eye.

Skillets

Liquid Crystal Thermometers: Experiments to do with liquid crystal temperature sensors.

Soap Film Painting

The soap film is a water sandwich - a layer of soapy water between two layers of soap molecules.

If you dip a finger into the soap solution you can push your finger through the soap film without breaking the film. The detergent molecules coating your hand join up with the molecules on the soap film.

If you tie a cotton string into a loop big enough to fit around your hand and leave a string "tail" then you can dip the string into the soap solution. Place it into the soap film and carefully use a dry pen to break the soap film inside the loop of the string then the surface tension of the soap film outside the string will pull it open, forming a nice circular hole in the soap film. The hole can be moved about. Too bad we can't do that with manholes in the street.

Is the soap film a liquid or a solid?

Blow on the soap film. See if you can blow just right to create a bubble which leaves the soap film and flies away on its own.

Shake the soap film and look at the pattern of waves created on its surface.

Soap Film in a Can: a small scale version of this activity

Soap Film Interference: Use 3x5 cards to model the interference that creates colors in soap films (High School Physics activity)

Soap film colors: The physics of interference colors in soap films. (College Physics Activity.)

Spectra

Build a Spectroscope: use a shoe box

Spectra exploration, use a diffraction grating to search for spectra in the world around you.

Project a Spectrum with an overhead projector

 Scientific Explorations with Paul Doherty © 2003 5 May 2003