Mystery Powders

Students perform five tests on five unknown white powders. Through these tests the students will learn how to determine the composition of each unknown. In the first part students learn what a positive test is for each unknown powder. Students then apply this knowledge in the second part to identify the unknown substances in a mystery substance.

     The unknown substances are sugar (turns brown when heated), cornstarch (turns black when tested with iodine), plaster (powder under hand lens and does not dissolve in water), salt (white crystals under hand lens and dissolves in water), baking soda (bubbles in vinegar).

     Make up mystery powders using two or more of the white powders. Have the students identify the mystery powders using the same tests.

     Baby food jars are excellent for the mystery powders. They will keep for a long time in the jars. Label the jars and keep a key.

MATERIALS:

     5 jars each containing a different powder
     water
     vinegar
     iodine
     1 candle in metal jar lid
     matches
     spring-type clothespins
     1 piece of aluminum foil
     chemplate
     6 plastic spoons
     toothpicks