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

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

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