Final answer:
Yeast, baking soda, baking powder, baking ammonia, air, and steam are all leavening agents used in baking to make dough rise. They produce gases, often carbon dioxide, that cause dough to expand and become light or airy.
Step-by-step explanation:
Yeast, baking soda, baking powder, baking ammonia, air, and steam are all agents that can be used to cause baked goods to rise, a process called leavening. These substances all have the ability to produce gas, often carbon dioxide, which gets trapped in the dough causing it to expand and become 'light' or 'airy'.
The process varies with the substance. Yeast, for instance, is a living microorganism. It metabolizes the carbohydrates in the dough, producing carbon dioxide and ethanol through fermentation. Baking soda (sodium bicarbonate) and baking powder react with other ingredients in a recipe to produce carbon dioxide. Baking ammonia (ammonium bicarbonate) also releases gas when heated, but it's less commonly used because it can leave a noticeable taste if not completely baked out.
Learn more about Leavening Agents