chemical leaveners reduce the density of baked goods by introducing carbon dioxide (CO2) into doughs and batters through in situ chemical reactions. The source of the carbon dioxide is bicarbonate ion, a negatively charged ion with the chemical formula HCO3-. When mixed with an acid in a wet dough or batter, the mildly alkaline bicarbonate reacts to form gaseous carbon dioxide and water in the form of steam. As with yeast leavening, the resulting gas bubbles create cavities in the batter, which are preserved when the batter sets up during baking, creating a less dense material. See yeast.
