Liquid crystal sheets, thermochromic fun!:
From Educational Innovations: BUY NOW liquid crystal thermometer sheet
Thermochromic Chiral Liquid Crystals: the thin layer changes color as the molecules of the liquid crystal change orientation and spacing during the phase transition from liquid (warm) to crystal (cool).
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From Educational Innovations: BUY NOW Polydensity Bottle Kit
Poly Density Puzzle: my favorite science brain teaser- white beads and blue beads "float" oddly separated beneath the surface of a clear liquid. If the contents are mixed by shaking the container, the white beads gather at the top and the blue sink to bottom! Adding to the mystery; after about 30 seconds the two layers of beads will have slowly moved back to the middle. What is your guess as to the physics behind this behavior?
Get some of these grow-spheres here:
From Educational Innovations: BUY NOW Growing Spheres
Poly-acrylamide Polymer Vanishing Act: these spheres of hydrophilic polymer have an almost identical index of refraction as that of water- thus when submersed they become invisible. Note the elasticity of these spheres from the way they bounce, while at the same time they refract their surroundings as a spherical lens. The super absorbent spheres start as hard crystals with a radius of 2mm and grow to 11mm when immersed in water. So much physics going on here!
Get this inexpensive device here:
From Educational Innovations: BUY NOW: Static Spheres
Click here for other static electricity devices
Static Spheres: triboelectric effect toy. The red acetate spheres are given an acquired net negative charge, and their mutual repulsion allows them to jump a centimeter or more as charge is manipulated on the PET plastic container. Bringing an object near the container momentarily moves electrons (charge) around creating repulsive forces (sphere v. sphere) and attractive forces (spheres and container) resulting in the observed motions. The red spheres interact with each other without coming into physical contact (as shown in 240 fps slow motion) as like charges repel. Shaking the system a bit allows the red spheres to pick up charge in the first place by colliding with the container.
Get this easy to assemble kit here:
From Educational Innovations: BUY NOW Simplest Motor Kit
Electric Motor: in its simplest form!- coil, magnet, and battery. The wire of the coil has an insulating coating- and this coating is carefully scrapped off one side on each end. When current passes through the coil it becomes an electromagnet and the permanent magnet repels it making it spin- as it turns the currents goes on and off depending if the copper posts are in contact with the bare wire (current on) or the still insulated wire (current off). I have motors with fewer parts- but they operate on more complex principles.
Available in "pro" metal version and colored rings version:
From Educational Innovations: BUY NOW Jitter Gyro Ring
From eBay: BUY NOW Color Jitter Gyro Ring
Jitter Gyro Ring: a 1990s skill toy craze out of New Zealand that features small rings that "roll" down a thicker steel ring and making a characteristic chattering sound as they go. Swiping the small rings gets them spinning and gives them angular momentum. Centripetal acceleration then keeps the inside of the small rings in contact with the steel ring so that they roll around as they descend (seen here in 240fps slow motion). The challenge is to rotate the large ring fast enough to keep the small rings in motion.
Samples available here:
From Educational Innovations: BUY NOW Ironwood Samples
Buoyancy Discrepant Event: wood that sinks and a rock that floats!- a study in density properties of ironwood and pumice.
Rave math fun for only $6.95!
From Educational Innovations: BUY NOW Twin Fan LED
Twin Fan Lissajous: two rotating fans with LED lights form Lissajous figures when spun around common axis. The rate and direction of spin determines the shape of the figure. With the image flash rate above the flicker fusion frequency (as it is here, above 16Hz) our vision perceives connected curves. Looks even more amazing in person!
This physics toy top is available here:
From Educational Innovations: BUY NOW Mystery Spinning Top
The amazing green magnetic viewing film is also available:
From Educational Innovations: BUY NOW Magnetic Field Viewing Film
Here is the 1974 patent showing the very simple circuit of this device. The spinning dipole (the top itself) induces a current in one of the coils, and this current is fed to the base of the transistor turning the electromagnet on when the top is near.
"Top Secret": this top will stay spinning for more than a week- because it is actually a motor! The top is a dipole magnet (as revealed by Magneview film) and the base has an electromagnet that gives the dipole a push when the top comes near the center. An ingeniously simple circuit consisting of only a battery, a coil, and a transistor, is activated when the spinning magnet nears the coil turning on the electromagnet to give a boost to the spin of the magnetic top.
Get a sample here:
From Amazon: BUY NOW Optical Calcite Crystal
From eBay: BUY NOW Optical Calcite Crystal
Get inexpensive polarizing filters here:
From Educational Innovations: BUY NOW Polarizing Filter Sheets
Birefringence in Calcite: the speed of light in a calcite crystal depends on polarization- the refractive index is different depending on the polarization orientation of the light transmitted through it. As a polarizing filter is rotated 90 degrees, one image appears and the other vanishes, showing that the polarization orientation of the light of the two images is indeed perpendicular. In addition the elegant rhombohedral nature of calcite crystals is obvious in this sample.
Available in many sizes and colors:
From Educational Innovations: BUY NOW Click Activated Resuable Heat Pack
From Amazon: BUY NOW Click Activated Reusable Heat Pack
Exothermic Crystallization Heat Pack: real-time instant crystallization of a supercooled solution. Solid sodium acetate melts at 137F (58C), but it will stay in liquid form as it cools to room temperature creating a supersaturated and supercooled state- the solution stays in the liquid form until a seed crystal, provided by clicking the metal disk, initiates the solidification. The resulting white crystal is actually quite hot; solid states have lower energy than liquid states and thus the difference in energy is given up as heat that raises the temperature back up to the melting temp, and you can see in the few seconds of the video that the temperature rises from 26C to 34C. This pack is reusable many times- just boil the pack until all the crystal is melted to reset.
Get some magnetic viewing film here:
From Educational Innovations: BUY NOW Magnetic Viewing Film
Magneview Flim: making the invisible visible and revealing the hidden physics of our everyday world. Microscopic cavities in this green film are filled with oil and tiny flakes of Nickel metal- like compass needles, the flakes align with the magnetic fields revealing the complexity of the north and south pole domains of these magnets. Two of the disk magnets have multiple north and south poles and look like gears with teeth- these are rotors from small motors.
Get one from these fine sources:
From Educational Innovations: BUY NOW Floating Ring Magnet Set
From Amazon: BUY NOW Floating Ring Magnet Set
Magnetic Levitation in 1D: a stack of dipole magnets. Note how the spacing between any two magnets is proportional to weight of how many magnets there are above the gap. Gravity vs Magnetism.
Get a set here!
From Educational Innovations: BUY NOW Bimetallic Jumping Disks
Bimetallic Jumping Disks: (wait for it!) slightly bowl shaped disks comprised of two thin fused sheets of different metals- each with a different coefficient of thermal expansion. If the disks are warmed to body temperature they will stay buckled if pressed- when they cool, they spring back into their original form with a sharp snap. Watch with sound on.
Get this similar demonstration kit here:
From Educational Innovations: BUY NOW
Ice Blocks Melt Demo
Ice Melt Demonstration: Wood or Aluminum- which will melt the ice fastest and why? Both blocks start at the same temperature (room temp) and have the same shape and volume. Swipe to reveal result shown in real time (not sped up!) Hint: Although both blocks are at the same temperature, the aluminum feels cool to the touch and the wood block feels warm. Those who have taken basic physics should have an advantage on this question- one block is an excellent insulator and the other a conductor.