Time's Up: inverse of the sandglass- tiny plastic beads are less dense than the water and thus ascend to the top of the container under the influence of a buoyant force in accordance with Archimedes' principle. This timer takes almost exactly 6 minutes to complete shown here at normal speed for the first half of this video, and the second half is condensed to 24 seconds in time-lapse.
I found this vintage apparatus on eBay. Here is a similar device made for classroom demonstrations (a bit pricey though):
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Wilson Cloud Chamber
Diffusion cloud chambers that use dry ice are more affordable:
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Diffusion Cloud Chamber
Wikipedia has nice descriptions of Am-241 and the history and operation of Wilson Cloud Chambers
Am-241 in Wilson Cloud Chamber: the typically invisible ionization tracks of alpha particles emitted from a radioactive source are revealed in this miniature expansion type cloud chamber. When an americium nuclei disintegrates it ejects a high speed cluster of protons and neutrons (2 of each) called an alpha particle which then plows through the air creating a trail of ions, tearing electrons off any nearby molecules it passes by. A rapid decrease of pressure (releasing the squeeze bulb) drops the temperature in this chamber allowing cloud formation. Alcohol droplets prefer to condense on ionized molecules/atoms and so reveal the tracks. Amazingly the synthetic element americium-241 is found in common smoke detectors, where a few micrograms will emit thousands of alphas per second. Of course please use great caution if you choose to mess around with any Am-241- it’s safe inside the smoke detector, much less so if removed.
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The Galton Board: 3000 steel balls fall through 12 levels of branching paths and always end up matching a bell curve distribution. Each ball has a 50/50 chance of following each branch such that the balls are distributed at the bottom by the mathematical binomial distribution. One of my favorite finds of 2018! An elegantly designed modern version of the Galton Box invented by Sir Francis Galton(1894) to demonstrate the Central Limit Theorem - showing how random processes gather around the mean. In addition the number of balls in each bin can be predicted by Pascal's triangle (printed on the face over the pegs).