Demonstrations for Chapter 10: Thermochemistry

54. Exothermic reactions give off heat to the surroundings: DH<0; sign is (-). Jack's demonstration uses heat from the hydration of quicklime, producing "slaked" lime, to fry an egg:

CaO(s) + H2O(liq) Ca(OH)2(s) + heat DH<0
quicklimeslaked lime

55. Endothermic reactions absorb heat from the surroundings: DH>0; sign is (+ Jack's demonstration makes use of the reaction between ammonium thiocyanate and barium hydroxide to freeze water):

heat + NH4SCN (s) + Ba(OH)2 NH3 + 2 H2O + Ba(SCN)2 DH>0

56. The "alcohol cannon" simulates the explosive events in a compression chamber of an internal combustion energy. The two nails act as electrodes.

57. Pyrotechnic display:

  1. strontium nitrate/potassium chlorate/charcoal/sulfur.
  2. barium nitrate/potassium chlorate/sugar.
  3. sulfur/charcoal/potassium chlorate/sodium oxylate.

58. Sugar and sulfuric acid. The dehydration reaction is violently exothermic, leading first to carmelization, and then carbonization.

59. Useful work performed by expanding gases: poping a rubber stopper; raising a book.