Baking soda fizzes with vinegar because sodium bicarbonate reacts with acetic acid to form carbon dioxide gas. The gas bubbles rise through the liquid, creating the visible foam.
Acid meets bicarbonate
Vinegar contains acetic acid, while baking soda is sodium bicarbonate. When they dissolve, the acid supplies hydrogen ions that react with bicarbonate. The immediate products include carbon dioxide, water and sodium acetate.
The fizz is not air released from the powder. It is newly formed CO₂ gas coming out of the liquid.
The foam depends on the mixture
More acid or bicarbonate does not automatically mean a taller foam. Concentration, temperature, container shape and the presence of soap or other ingredients affect how long bubbles survive.
The reaction can be vigorous in a small vessel, but the total gas is limited by the amount of reactants available.
The same chemistry can leaven food
In dough, bicarbonate reacts with an edible acid and produces CO₂ that becomes trapped in a batter. Heat also changes the bubbles and sets the surrounding structure. A volcano demonstration shows the gas clearly; baking uses the same basic reaction more carefully.
Chemistry explains both the spectacle and the texture.
Sources and evidence
- NC State University — Baking soda and baking powder ↗
Acid-base reaction and carbon dioxide production.
- American Chemical Society — Baking chemistry ↗
Bicarbonate, acids and gas formation in food.
Sources consulted: 9 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Added original explanatory comparisons, source-linked evidence and a reader-focused example.