Thermodynamics

The title is video link (where available). PDF file is below the description.

  • Chemical Traffic Light – Add NaOH, glucose, and indigo carmine to water in an Erlenmeyer flask. The solution starts green, and when the flask is open to the air, the solution gradually changes to red and then to yellow. Seal the flask and give it a light shake to turn the solution red, and give it a hard shake to turn it green. Repeatable! Shows how a reaction’s spontaneity and color change are driven by Gibbs Free Energy and oxidation-reduction cycling.
  • Combustion of Ethanol Vapors – Allow a small amount of ethanol to vaporize in a large carboy, pour out the excess liquid, and hold a lighted splint to the mouth of the container – the impressive reaction also demonstrates the flammability of organic vapors. Emphasizes energy release from combustion, transformation of chemical energy → thermal energy.
  • Crystallization of 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.
  • Elephant Toothpaste – Demonstrate the decomposition of 30% H2O2 in the presence of dishwashing liquid and KI, producing an upsurge of steaming foam. Combines enthalpy and entropy increase (gas formation).
  • 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.
  • Iodine Clock – Perform the iodine clock reaction with three different initial concentrations of IO3–. Emphasizes the chaos before order and how entropy increases even in reactions that end in order.
  • Squashing pop cans with atmospheric pressure – Use atmospheric pressure to squash pop cans. It’s an awesome way to show phase change, pressure drop, and how equilibrium shifts.
  • Thermite – Perform the exothermic thermite reaction, in which Al and Fe2O3 react to produce molten iron.