It was not until the middle of the 1800' s that people started using chemicals to put air into breads and cakes.Today, instead of yeast, we often use either baking soda or baking powder-sometime both. It takes much less time to bake with them. Batters, such as those used for pancakes and certain cakes, contain much more liqid than does the bread dough made with yeast. These batters are so thin that slow-acting yeast cannot trap enough air to make bubbles. That's why we use chmicals.