Whats the difference between baking powder and bicarbonate of soda?

Baking soda and bicarbonate of soda are the same in Australia.  Baking powder is not the same as bicarbonate of soda although powders are leavening agents. When included in a cake mixes and batter then beaten, the leavening agent causes air bubbles  to expand when cooked will  ‘rise’. Bicarbonate of soda is a pure leavening agent that needs moisture  and an acidic ingredient for the chemical reaction to take place to make food rise.  Bicarbonate  is often used in recipes where there is already an acidic ingredient  such as lemon juice, chocolate, buttermilk or honey.

Baking powder  contains bicarbonate of soda  plus the acidic ingredient called cream of tartar.  It has a neutral taste compared to bicarbonate of soda which has a tangy taste.  Baking powder  is often used in recipes that have other neutral tasting ingredients, such as milk.

Bicarbonate of soda makes a very specific texture not achievable with baking powder. It is very important to sift bicarbonate of soda well as it gets lumpy and to use very exact measures.