The classic kitchen science experiment of mixing baking soda and vinegar is a simple, engaging way to create a visible, dense gas. This popular DIY demonstration illustrates how two common household substances react to produce something entirely new. The resulting “fog” is not actually a mist of liquid water, but a heavy, invisible gas that settles and can be manipulated. This activity offers a hands-on look at acid-base reactions and the properties of gas density.
Materials and Instructions for the CO2 Effect
To create the visible gas effect, you will need baking soda, white distilled vinegar, a deep, clear container (like a tall glass or pitcher), and a small cup. Place about two tablespoons of baking soda into the bottom of the deep container. This container allows the heavy gas to collect and pool inside.
Next, pour approximately one-half cup of white vinegar into the small cup, which serves as your dispensing tool. Quickly pour the vinegar directly onto the baking soda; the mixture will begin to fizz vigorously. This effervescence signals the chemical reaction starting and the carbon dioxide gas being generated.
As the bubbling slows, the colorless, dense gas collects at the bottom of the container. Gently tilt the container and “pour” the invisible carbon dioxide over the edge and onto a surface, such as a lit candle. The gas, which is heavier than the surrounding air, flows downward and extinguishes the flame, demonstrating the presence of the invisible “fog.”
Understanding the Chemical Reaction
The dramatic fizzing is caused by an acid-base reaction between sodium bicarbonate (baking soda) and acetic acid (vinegar). Baking soda is a weak base, and vinegar is a dilute solution of acetic acid. When these two substances combine, a double displacement reaction occurs, initially forming sodium acetate and carbonic acid.
Carbonic acid is highly unstable at room temperature and immediately decomposes into two more stable compounds. This decomposition yields water and carbon dioxide gas (\(CO_2\)). The rapid production and release of this gas causes the bubbling and fills the container.
The gas behaves like a pourable “fog” because of its high density compared to the surrounding air. Carbon dioxide is approximately 1.5 times denser than air. Because of this greater mass, the gas sinks and pools at the bottom of the container, much like a liquid. When the container is tilted, the heavy carbon dioxide flows out and down, displacing the lighter ambient air.
Safety Protocols and Experiment Tips
Though this experiment uses common household items, simple safety precautions should be followed, including adult supervision. Always wear eye protection to guard against accidental splashes from the vigorous reaction. The resulting carbon dioxide gas is harmless and can be released safely into a ventilated room.
The final liquid product—a solution of water and sodium acetate—can be safely poured down the drain. To enhance the visual effect, you can add a few drops of food coloring to the vinegar before mixing. Performing the experiment in a location free of air drafts will help the heavy carbon dioxide settle and prevent it from dispersing too quickly.