What's In A Name?

Potassium chloride is addded to one glass cylinder containing water. Potassium chlorate is added to another. A dropperful of silver nitrate is added to each cylinder. Silver chloride precipitates in the cylinder containing KCl, but not in the other. In the second part of this demo, a test tube containing KCl is heated and a small piece of "Gummi Bear" is added. Nothing happens. But when the test tube containing KClO3 is heated, it melts. When the piece of "Gummi Bear" is added it bursts into flame as it is violently oxidized. 

Curriculum Notes 

This demo is useful when the rules of inorganic nomenclature are being introduced. It emphasizes the importance of the anion suffix in determining whether a polyatomic ion is being specified.

Lead Time 
One day of lead time is required for this project.
Discussion 

Most silver salts are insoluble. The nitrate and chlorate salts are exceptions, so the chloride ion will precipitate silver ion, whereas the chlorate ion will not.Gummi Bears are mainly sugar which is violently oxidized by the hot KClO3The products are probably mainly KCl, CO2, and H2O.Warning: The ethical ramifications of research on Gummi animals are very controversial. Many Gummi researchers have recieved formal complaints from the SPCGA (Society for the Prevention of Cruelty to Gummi Animals) and a few have had their labs ransacked by the GLF (Gummi Liberation Front). This scientist believes that Gummi research must continue as long as there is hope that Gummi research may lead to cures for human diseases such as GDS (Gummi Deficiency Syndrome). At the same time, every reasonable measure must be taken to ensure that Gummi suffering is kept to a minimum.

Materials 
  • 2 10g samples of KCl in 25x200mm stoppered test tubes
  • 2 10g samples of KClO3 in 25x200mm stoppered test tubes
  • 2 500mL glass cylinders filled most of the way with distilled water
  • 2 long stirring rods
  • dropper bottle containing 0.1M AgNO3
  • propane torch
  • test tube clamp
  • 2 250mL Erlenmeyer flasks
  • 1 Gummi Bear
  • 3 Petri dish bottoms (or tops)
  • spatula
  • forceps
  • large bell jar
Procedure 

Part 1

  • Hold up a test tube of each substance and ask students to observe their physical appearance.
  • Pour one of the test tubes of each of the substances into the glass cylinders. (The KCl into one and the KClO3 into the other.) Stir to dissolve.
  • Add a dropperful of AgNO3 solution into each of the cylinders.
  • A precipitate forms in the cylinder containing the KCl. There is no visible reaction in the other.

Part 2

  • Using the tongs, hold a test tube containing KCl in the burner flame for a minute or so. Insert the test tube into an Erlenmeyer flask sittng on an inverted Petri dish bottom. The Petri dish serves to insulate the table top from heat.
  • Cut a Gummi Bear in half and drop it in the test tube. Nothing happens other than the Gummi Bear melting and sizzling a little.
  • Repeat the procedure using KClO3. Heat it until the powder in the tube is completely melted. Be careful when you drop the Gummi Bear in because this time it will burst into flame.
  • Carefully place the bell jar over the flaming reaction mixture to contain the fumes.
Safety Precautions 
  • Silver nitrate and potassium chlorate are strong oxidizers. Avoid contact with flammable materials. If melted potassium chlorate comes into contact with any flammable amterial it will spontaneously burst into flame.
  • Be careful handling the test tube and flask after the violent oxidation reaction. The test tube will be extremely hot! Let the apparatus cool before handling.
  • Potassium chlorate and aqueous silver nitrate are strong oxidizers. Wash immediately with soap and water if any gets on your skin. Flush eyes immediately with water if any gets in your eyes.
  • Make sure that the demo are is clear of flammable substances. Have a fire extinguisher close at hand in case of fire.

© Copyright 2012 Email: Randy Sullivan, University of Oregon Chemistry Department and UO Libraries Interactive Media Group