April Altott

Instant Suds

Science Concept: A chemical reaction between citric acid and baking soda will create carbon dioxide gas.

Materials & Pre-Demo Preparation:

30 mL dish washing soap

120 mL warm water

9 g of baking soda*

3 g of citric acid*

* you could replace those and use just an Alka Seltzer

* another modification would be to use lemon juice for the citric acid.

vinegar

tall cylinder or 125 mL erlenmeyer flask

paper towels

stirring rod

Before the demonstration, measure out 9 grams of baking soda and 3 grams of citric acid and place in separate beakers. Get warm water from the sink only a minute or two before the demo, so that the water will be warm at the time of the demo. Also, when doing the demo, place the beaker on top of some paper towels or a pie plate to catch any suds that may flow over the top of the beaker.

Directions: In the glass beaker or flask, mix the 30 mL of dish soap with 120 mL of warm water. Add 9 g of baking soda, and mix well. Once it is mixed up, sprinkle citric acid on the top of the liquid and mix together. Suds should begin to appear. If the reaction appears to be slow, you may add small amounts of vinegar to increase the foam production.

Introduction & Commentary: How many of you like to take bubble baths? Do you like a lot of bubbles, or only a little? If you're like me, lots of bubbles are the most fun. I'm going to show you a trick where I can make lots of bubbles without using bubble bath or a lot water.

Explanation: Mixing warm water, soap detergent, and baking soda together does not form a chemical reaction. When citric acid is added to the mix, however, a reaction occurs in which carbon dioxide is formed and gives rise to the bubbles seen in the suds. When the citric acid is added to water, a reaction occurs in which hydrogen ions from the acid are released. These hydrogen ions then react with the baking soda to produce carbon dioxide gas, which disperses throughout the water and creates the suds. The production of foam may be increased by the addition of a liquid acid such as acetic acid in vinegar. The citric acid as a solid may be slow to dissolve, hence the liquid has a faster reaction. Any acid produces hydrogen ions which is the main cause of the reaction.

citric acid + water (H₂O) --------> hydrogen ions (H⁺) + citrate ions

hydrogen ions (H⁺) + baking soda (NaHCO₃) ----> carbon dioxide (CO₂) + water (H₂O) + sodium citrate

Safety Precautions: There are no particular safety precautions for this experiment.

Waste Disposal: Empty the contents of the beaker down the sink.

Reference: Unknown