EXOTHERMIC AND ENDOTHERMIC REACTIONS
HERBERT TARNOR DU SABLE HIGH SCHOOL
4934 S. WABASH AV.
(1) Students are to observe several exothermic and endothermic reactions.
(2) Students are to determine the changes that take place in a chemical
reaction; to observe how fast a reaction is taking place and what factors
influence a chemical reaction.
(1) A picture puzzle.
(2) Two burettes, ring stand and clamp, plastic rod, fur, water, alcohol.
(3) Model of a crystal, nails, wooden blocks, and magnets.
(4) Dry ice (CO2), two 1000 ml graduated cylinders, red and blue dyes,
pneumatic trough, gas bottle, rubber tubing, fish tank, candles, steps.
(5) Nitrogen triiodide (NI3) 2-3 g, ring stand, 3 iron rings, three sheets of
filter paper which are larger than the rings, feather, 2 m pole.
(6) Potassium chlorate (KClO3) 6 g granulated sugar 2 g, 1 drop H2SO4, ring
stand with metal base.
(7) One 50 ml beaker with 20 g barium hydroxide (Ba(OH)2.8H2O). One 50
ml.beaker with 10 g ammonium thiocyanate (NH4SCN), wooden block.
Safety glasses, 3 test tubes with stoppers, marking pencil, test tube holder,
10 ml graduated cylinder, small spatula, stirring rod, thermometer. Reagents:
Sodium thiosulfate crystals, 18 M (concentrated) sulfuric acid (H2SO4), ammonium
(1) Drop the picture puzzle and allow the pieces to scatter. Discuss entropy
and the Second Law of Thermodynamics (basically that no process can occur unless
there is an increase in the disorder in the universe when it happens).
(2) Allow the water to stream from the burette, rub the plastic rod with fur
and hold it close to the stream. Explain that water is polar and is being
attracted by the electrons on the plastic rod. Repeat using alcohol and carbon
(3) Display the model of a crystal. Use a magnet to pull the ions apart in
the crystal lattice, and show the point of attack of solvent molecules (the exposed
corners), pointing out that the solvent molecules envelop the ions and actually
tear the crystal apart.
(4) Collect the CO2(g) and show the effect when it is poured in to the fish
tank where the candles are burning on steps.
(1) Label a test tube #1. Fill a test tube nearly full a sodium thiosulfate
crystals. Record the temperature. Add just enough drops of water to make the
crystals look wet half-way up their height. Now warm the tube gently, with steady
swirling, over a burner flame. The wet crystals will melt rather readily. When
the tube contents are fully liquid, and uniformly stirred so no concentration
waves show, record the temperature. Set the tube aside to cool (if care is used,
it can even be cooled in cold water, though in this case premature crystallization
may occur). We now have a supercooled liquid. Even though the liquid is far below
the freezing point (or saturation temperature), the sodium thiosulfate will not
readily crystallize unless some kind of nucleus is provided. When the tube is
cooled, drop a single crystal of sodium thiosulfate into the tube-it makes no
difference how tiny. Immediately crystals will start spreading from this nucleus.
When the reaction is completed the tube will be hot. Record the temperature.
(2) Label a test tube #2. Place 2 ml of tap water in the test tube. Add 10 drops
of concentrated sulfuric acid (H2SO4) to the water. Feel the tube and record the
temperature. Carefully wash off the thermometer with tap water.
(3) Label a test tube #3. Place 1 spatula of ammonium chloride (NH4Cl) in th
test tube. Add 2 ml of water. Stopper and shake the test tube. Record any change
in the temperature of the solution and discard the materials.
Kerkut, G.A. Implications of Evolution (1960).
Morris,Daniel Luzon.The Dynamic Equilibrium Approach to Teaching Chem-
istry (West Nyack, New York, Parker Publishing
Company,Inc.: 1974), p. 72.
Olmsted, Michael P. Chemistry Teacher's Guide (West Nyack, New York,
Parker Publishing Company,Inc.:1972),pp.116f.
Shakhashiri, Bassam Z. Chemical Demonstrations: A Handbook for Teachers
of Chemistry, Vol.1 (Madison, Wisconsin, The University
of Wisconsin Press: 1983), pp. 10f.,96-98.
(NO AUTHOR) "Life on Earth: From Chemicals in Space?" Chemical
and Engineering News (19), Nov. 19,1973, pp.21-22.
Brinkman, R. T. "Dissociation of Water Vapor and Evolution of Oxygen
in the Terrestrial Atmosphere," Journal of Geophysical
Research (74), Oct.20, 1969, pp.5355-5368.
Carruthers,George R. "Apollo 16 Far-Ultraviolet Camera/Spectograph: Earth
Observations."Science (177), 1 Sept. 1972, pp. 788-
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