Why Does Cutting an Onion Make You Cry?
Description: This phenomenon can be used to illustrate both chemical reactions and the particle nature of matter. Onions gather sulfur from the ground to form large organic compounds. When the cells in an onion are breached (during cutting or eating) they release sulfenic acid which becomes a sulfur containing gas that eventually reaches your eye. Your eyes produce tears to remove the irritant. Students could speculate on how the irritant reaches your eyes and even investigate possible solutions to this problem. This phenomenon was submitted by Brian Babulic.
Web Resource: Science News for Kids - Informational Text Article
Fire Piston
Description: Fire pistons have been used for hundreds of years as a fire starter. Tinder is place in a seal tube and a piston is rapidly pushed into the tube. The air is compressed increasing the pressure and temperature until the ignition point of the tinder is reached. A diesel engine works in a similar fashion. This phenomenon can be used to introduce the particle model of air and temperature as a measure of the kinetic energy of particles.
Web Resource: Fire piston - Wikipedia
Milk and Soap Experiment
Description: Milk is made up of water, fat, and proteins. Each of these molecules have charges and are held together by intramolecular forces. When the dish soap is added to the plate it quickly disperses across the surface as it is attracted to the water molecules and the food coloring is pulled along. This could be used as an anchoring phenomenon on matter, materials, or intramolecular forces.
Web Resource: Colors on the Mooooove - ACS
Supercooled Water
Description: Supercooling occurs when the temperature of a liquid is lowered below the freezing point without forming a solid. In the case of water it needs a seed crystal or a nucleation site to start forming ice. If the water has been filtered through reverse osmosis or chemical demineralization it can be safely cooled below the freezing point. Simply shaking the bottle forms solid ice.
Web Resource: Supercooling - Wikpedia
Indestructible Coating - Polyurea
Description: In this video a watermelon is covered with a polymer and survives a drop from a large tower. The polymer is formed when two reactants join to make a flexible and durable polymer known as a polyurea. The chemical reaction is exothermic, releasing heat as the reactants combine. This phenomenon could be used in a unit on chemical reactions, extended structures or chemical engineering. The company Line-X uses this polymer to make bed liners for pickup trucks.
Web Resources: Polyurea - Wikipedia, Line-X
Aerogels - World’s Lightest Solids
Description: Aerogels are a group of synthetic materials that are incredibly light and also amazing insulators. They have numerous applications such as insulators in electronics. Aerogels were used as thermal insulators in the Mars Rover and also act to filter space dust. This phenomenon could be used as an application of chemical engineering or as an example of a thermal insulators.
Web Resource: Aerogel - Wikipedia
Reusable Heat Packs
Description: This phenomenon uses a supersaturated solution of sodium acetate. Clicking the metal disc releases a small number of crystals of sodium acetate which act as nucleation sites for the crystallization of the sodium acetate into a hydrated salt. Energy is released from the crystal lattice. The heating pack can be placed in boiling water and the sodium acetate can be dissolved again. This phenomenon shows how bond energy can be released. It also shows the importance of chemical engineering and could lead to a section where students design a device (or application) of their own.
Web Resource: Chemical Heat Pack - Wikipedia, Snappy Heat - Amazon
The Collapsing Train Car
Description: The collapsing train car can be used as an anchoring phenomenon on a unit related to the structure and properties of matter. The macroscopic implosion is caused by a decrease in pressure within the train car and air pressure crushing the car. To fully understand this phenomenon students must understand what is going on at the microscopic level. This phenomenon can be demonstrated at a smaller scale in the lab using an empty soda pop can (containing a small amount of water) that is heated and then inverted in water.
Ice Cube Spikes
Description: Ice cube spikes form when the exterior of the ice cube freezes first and the expanding water from the inside is forced out through a small hole or weak spot in the exterior. The phenomenon can be used to show the reversible change of freezing in elementary or the intermolecular forces between molecules in high school chemistry.
Web Resource: Spikes on Ice Cubes
Precious Plastic
Description: Precious Plastics was created in 2013 by Dave Hakkens. It is a website that shares DIY plans for building machines that can recycle plastic. Plastic is recreated through a non-reversible reaction and if it isn't recycled this valuable plastic is often lost forever when it is dumped in a landfill. These plans have spawned a community of DIY plastic recyclers around the world. Even though most students lack the ability to construct these machines it may lead to simple projects like the Ecobricks project linked below.
Web Resources: Precious Plastic, Ecobricks - plastic, solved
Slime
Description: Everyone loves slime...especially elementary students. This phenomenon is a great introduction into chemical reactions. The properties of the reactants can be compared to the properties of the products to show that a chemical reaction has occurred. In high school the chemistry of polymers and cross-linking can be explored through slime.
Web Resource: The Science of Slime - American Chemical Society
