Baking soda or Sodium bicarbonate it reacts with other components to release carbon dioxide, that helps dough "rise".
Helps Rise
The recipe that I use calls for baking soda.
To replace for example 3 teaspoons of baking powder with baking soda, mix 1 teaspoon of baking soda with 2 teaspoons of cream of tartar.
No, baking soda cannot substitute for baking soda because they are the same thing. Baking soda is just another name for sodium bicarbonate.
yes indeed
Baking soda will cause things to rise also. Muffins are smaller so there is not as much need for lift. Baking powder will give more rise than soda. Whoever created the recipe chose to use soda instead of baking powder.
If the recipe calls for it, yes.
If too little baking soda is used, the product will not rise properly.
Add a teaspoon of baking soda for each cup of sour milk.
The original Nestlés Toll House cookies (chocolate chip cookies) recipe calls for baking soda, not baking powder. There is no substitute for baking soda or baking powder in a recipe. You have to have it.
Baking powder and baking soda are often used together in recipes in order to add lift to the final product. Because baking soda is a base and commercial baking powder is generally slightly acidic, they are often used together to neutralize both each other the other ingredients of the recipe. Yes baking powder and soda can both be used in the same recipe.
Baking powder is a mixture of baking soda, starch and an acid (often tartar) to activate the baking soda. Since baking soda is already in the baking powder, it is possible you will not need any additional baking soda. Baking powder and baking soda are used to "raise" or puff up the pastry - too little and it will not raise properly...too much and it will taste like soda. If you do not have a specific recipe, you will need to experiment.