Obtain a package of Alka-Seltzer, an antacid, from the local drug store: Why does Alka-Seltzer foam and bubble when dissolved in water? Which ingredient is the antacid?

When Alka-Seltzer is dissolved in water, a chemical reaction occurs between the ingredients, primarily sodium bicarbonate (baking soda) and citric acid. This reaction produces carbon dioxide gas, which forms bubbles and causes the foaming effect. Understanding this reaction is crucial to grasping why the product behaves as it does in water.

Alka-Seltzer contains sodium bicarbonate, which acts as a base, and citric acid, which is the acid component. When these two substances react, they neutralize each other, resulting in the formation of water, carbon dioxide, and sodium citrate. This neutralization is essential for the antacid properties of Alka-Seltzer, as it helps to alleviate stomach acidity.

The foaming and bubbling of Alka-Seltzer in water is primarily due to the production of carbon dioxide gas. As the citric acid and sodium bicarbonate react, carbon dioxide is released, creating bubbles that rise to the surface. This gas production is a key indicator of the chemical reaction taking place and is a visual cue of the antacid's effectiveness.