When baking soda is mixed with vinegar, they undergo an acid–base reaction that fizzes, forming carbon dioxide gas, water, and a salt called sodium acetate.

Quick Scoop

What’s physically happening

  • You see bubbles and fizz because carbon dioxide (CO₂) gas is released.
  • The mixture may foam up or overflow if there’s a lot of each ingredient, since the gas gets trapped in the liquid to make a bubbly foam.
  • If you capture the gas in a balloon or sealed setup, it can inflate because CO₂ takes up space and has mass.

What’s chemically happening

  • Baking soda is sodium bicarbonate (NaHCO₃), which behaves as a base.
  • Vinegar is water with acetic acid (CH₃COOH), which behaves as an acid.
  • When they react, atoms rearrange to form:
    • Carbonic acid, which quickly breaks down into water and carbon dioxide gas.
* Sodium acetate (a type of salt) dissolved in the remaining water.

Overall, the key thing that “happens” is a visible, fizzy chemical reaction where an acid and a base are turned into new substances plus lots of CO₂ bubbles.