Caroline Imreibe

Production of Foam

Concept: The production of CO2 gas in laundry detergent creates foam.

Materials:

Solution A: 1 g laundry detergent

7 g aluminum sulfate* - This may be purchased in the spice section of grocery story as alum.

25 mL water

Solution B: 5 g baking soda

25 mL water

Demo:

1.) Pour the contents of solution A into solution B.

2.) Mix quickly.

Introduction: In solution A, I have laundry detergent, aluminum sulfate, and some water. In solution B, I have household baking soda and some water. Watch as I pour A into B.

Explanation: Two separate reactions occurred. First, combining aluminum sulfate and water produces positively charged hydrogen ions, in the form on sulfuric acid in the equation below. These hydrogen ions act as an acid. The hydrogen ions react with the baking soda to produce CO₂ gas which is dispersed throughout water to create the foam. The detergent is added to help capture the CO₂ bubbles in the foam.

Al₂(SO₄) + HOH ----> H₂(SO₄) + Al(OH)₃

H₂(SO₄) + 2 NaHCO₃ ----> 2 CO₂ + Na₂SO₄ + 2 HOH

Safety: Handle wet glassware with caution.

Waste Disposal:

Dispose of remaining liquids and foam in sink.

Reference: Summerlin, L, Ealy, J, Chemical Demonstrations, American Chemical Society, 1985, p.133