Energy and Chemical Reactions

 

Black Carbon Snake – Show the dehydrating properties of concentrated H2SO4 by adding it to sugar in a tall beaker to produce a black “snake” of carbon that grows out the top of the beaker.

Combustion of Candy – Contrast the rate of oxidation of sucrose in the body (by eating some candy) with the oxidation of sucrose by KClO3 (as shown by dropping some candy into molten KClO3) producing steam and a lavender flame. Body temperature is ~37°C, and the melting point of KClO3 is 368°C.

Combustion of Magnesium in Dry Ice – Demonstrate the combustion of magnesium in dry ice, resulting in a luminous effect as well as the production of MgO and elemental carbon.

Endothermic Reaction – Shake solid Ba(OH)2 • 8 H2O with solid NH4NO3 to produce an aqueous mixture of Ba(NO3)2 (s) and NH3 (aq). The reaction is endothermic enough to freeze the flask to a wet piece of cardboard. Alternatively, a digital thermometer can be used to record the temperature change.

Glycerin and Potassium Permanganate – Pour glycerin over KMnO4 (s) to initiate a spontaneous combustion accompanied by smoke, sparks, and a lavender flame.

Hot and Cold Packs – Introduce the terms exothermic and endothermic with a demonstration of the dramatic temperature changes accompanying the dissolution of CaCl(s) and NH4NO(s) in water.

Luminol Ammonia Fountain – Take advantage of the solubility of NH3 due to hydrogen bonding to create a chemiluminescent fountain in an upturned round bottom flask.

Luminol Reaction – Pour solutions of luminol and H2O2 into a tall glass spiral to produce a beautiful chemiluminescent reaction. The light-emitting species is the dicarboxylate ion, aminophthalate, the product of the oxidation of luminol with H2O2. (Includes recipe for Crime Scene Luminol)

Money to Burn – Soak a dollar bill in a water-alcohol mixture and then light it with a match; the high specific heat of water keeps the combustion temperature low enough to prevent burning the bill.

Production and Combustion of Carbon Monoxide – Combine concentrated sulfuric and formic acids to produce carbon monoxide, then ignite the gas, showing that it burns with a blue flame.

Sound – Tap a very small pile of red phosphorus and KClO3 with a hammer to show a reaction that produces light, sound, and heat, and recreates on a larger scale the reaction that occurs when you strike a match.

Supersaturated Sodium Acetate – Add a tiny crystal of sodium acetate to a 2 L flask of a super-saturated solution to cause the solid to crystallize out, leaving almost no liquid – this demonstration is beautiful and dramatic, as well as being quite exothermic. Alternatively, you can pour the solution slowly over a single crystal to build up a column of solid sodium acetate.

Thermite – Perform the thermite reaction, in which Al and Fe2O3 react to produce molten iron.