Baking Basics - Yeast

[Gituli]

As the yeast consumes sugars present in the flour, it releases carbon dioxide gas, forming thousands of teeny tiny air pockets inside the dough and causing it to rise. Once you pop that dough in the oven, those air pockets heat up and further expand, and a phenomenon known as oven spring takes place. Finally, as the gluten gets hot enough, it sets into a semisolid form, giving structure to the bread, and turning it from wet and stretchy to dry and spongy.

[Gituli]

Baking Powder consists of --
mixture of a carbonate or bicarbonate and a weak acid
30% sodium bicarbonate, 5-12% monocalcium phosphate, and 21-26% sodium aluminum sulfate.

Uses
This is used instead of yeast for end-products where fermentation flavors would be undesirable. It does not require an external acid in order to activate.

[Gituli]

Baking Soda = Sodium bicarbonate (NaHCO3)
Crystalline but often appears as a fine powder.

Uses
Used in baking as a leavening agent.
It reacts with acids immediately upon contact to produce carbon dioxide.

Washing soda = Sodium carbonate (Na2CO3)
It is water-soluble sodium salt of carbonic acid.
It is used as a "Water Softener".