Foam Production
I. INTRODUCTION: The use of simple easy to find chemicals can result in a dramatic demonstration of production of a chemical foam. A variety of skills and topics can be covered in this activity including: lab safety and behavior, wafting to smell chemicals, observation skills, measurement and mathematics skills.
II. MATERIALS: Baking soda, alum, unflavored gelatin, vinegar, plastic spoons, two plastic cups for each student, food coloring (optional).
- a. Each student places one spoonful of each solid
into one of the cups (it can be labeled "1" or "solids").
To reinforce appropriate lab behavior and safety, be sure that different
spoons are used for each solid - although mixing them will not adversely
affect the results.
- b. Each student will put three teaspoons of vinegar in the "2" or "liquid" cup. If desired, some food coloring can be added to the vinegar. Demonstrate how to waft the odor of the vinegar toward the nose in order to safely smell the chemical.
- c. Once the materials have been collected, place the solids cup on several sheets of newspaper. To build the excitement, have all the students mix their solids together well and wait to add the liquids all at the same time. On the count of three, they may pour the liquid into the solid cup and stir.
- d. As the foam is produced and spills over the sides, they may continue stirring. If the bubbles are not overly stirred, they will last a long time. Once the reaction has stopped, the students may want to start it again. Give them access to the chemicals and they will realize that the addition of more vinegar will indeed restart the reaction.
- b. Each student will put three teaspoons of vinegar in the "2" or "liquid" cup. If desired, some food coloring can be added to the vinegar. Demonstrate how to waft the odor of the vinegar toward the nose in order to safely smell the chemical.