New Ideas for Old snacks
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The original gas model used rat cages to hold ping-pong balls. Shaking the cage modeled solids, liquids and gases. Rat cages are now expensive and hard to find. We’ve recently discovered inexpensive open-top wire baskets at Target, Walmart, and Orchard Supply that can be topped with cardboard and filled with a dozen or so ping-pong balls. The cardboard acts as a sound board that let’s you hear the impacts of the moving balls. You can stick fingertips through the holes in the wire and feel the impacts of the balls. Shaking faster makes impact sounds more frequently, and also makes impacts with more impulse.
Math root: Increasing the temperature of a gas increases the velocity of the gas. Pressure is proportional to the number of times per second that a molecule hits a wall that is proportional to the velocity of the molecule. It is also proportional to the strength or impulse that the molecule imparts to the wall which is also proportional to the velocity. So the pressure is proportional to the velocity of the molecules squared. The temperature is proportional to the kinetic energy of translational motion per molecule. This means that since the kinetic energy is 1/2mv^2 that the temperature is proportional to the square of the velocity. Thus the pressure is proportional to the temperature.
Original Snack Gas Model
Soap film in a can
The original snack used film cans which are now hard to find.
Eric Muller discovered that black ABS plastic irrigation pipe caps and couplers can be used to make the soap film colors visible.
We use Blue Dawn dishwashing liquid mixed with distilled water in a ratio of 1 part dawn to 10 parts water. The solution is allowed to sit overnight.
It is important to put a white paper underneath the soap film container to reflect light upward off the film and into your eye.
This is a true nanoscale activity the thickness of the soap film when it shows colors is usually under 1000 nanometers.
Original Snack Soap Film in a can
Explanation of original snack.
The original incandescent party bulbs have been replaced by much better Compact Fluorescent Party bulbs, and more recently by colored LED bulbs. (In general these new bulbs do not have adjustable brightness, and the compact fluorescent green is often too bright.)
Original Snack Colored Shadows
Teacher Institute Video on Kahn Academy
Polarized Light Model.
A model for polarized light and polarizers can be made using coiled phonecords and PVC tubes.
New Snack Polarized Light Model
Digital printers are now good enough to print out gray step exhibits.
It may take some playing around with print settings to get a good print-out.
Original Snack Grey Step with new high-resolution gray step image included.
The use of Pizza pans to contain the spinning cylinders makes this activity much easier.
Original Snack Sprotating Cylinder
Scientific Explorations with Paul Doherty
6 March 2015