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
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
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
Reaction in a Bag
Description: This video shows a chemical reaction of sodium bicarbonate (baking soda), calcium chloride (road salt), and an indicator phenol red. The chemicals react to form calcium carbonate, sodium chloride, and carbon dioxide gas. This changes the pH inside the bag resulting in a color change in the phenol red. As much air as possible should be removed from the bag as possible to show the production of the gas. This could be used as an example of chemical reaction that releases energy (exothermic). Since the bag is sealed it could be massed before and after to show the conservation of mass (atoms). This phenomenon was submitted by Brian Babulic.
Web Resources: Reaction in a Bag - Flinn Scientific, American Chemical Society - Explanation
Burning Steel Wool
Description: This is an excellent phenomenon to discuss chemical reactions and the conservation of mass. Steel wool is burned leading to an increase in mass. When doing this in class show the students the burning steel wool to begin with and have them predict the change in mass. Most students believe the mass will either increase or decrease. This phenomenon can be used at the beginning of a unit on chemical reactions and students can investigate their individual models. (e.g. mass comes from fire, oxygen, carbon, etc.)
Web Resources: Combustion of Iron Wool - CFNS Experiment 36
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
Will It Conduct?
Description: Conductivity is an excellent way to classify material by their observable properties. Conducting material (e.g. metal), non-conducting material (e.g. plastic), and semi-conducting material (e.g. graphite) should all be used. A simple circuit with a lightbulb is used to determine the conductivity of different materials. These properties can be used to determine if a chemical change has occurred by testing before and after substances have been mixed. These properties can also be used in the design of an engineering solution.
Web Resource: Teach Engineering - Conductivity
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
Elephant Toothpaste
Description: Elephant toothpaste is a dramatic chemistry demonstration that involves the decomposition of concentrated hydrogen peroxide (H2O2) into water and oxygen. Potassium iodide is used as a catalyst to speed up the reaction. Soap is added to trap the escaping oxygen gas and food coloring is often added to the experiment. This phenomenon can be using in elementary science classes to illustrate non-reversible reactions and can be studied in more detail in middle and high school.
Web Resource: Elephant toothpaste - Wikipedia
