Mandy - from England, UK
Baking soda is the same as bicarbonate of soda. It is used when there is an acidic ingredient, like chocolate or sour cream in the cake batter. The reaction with causes your cake to rise happens immediately so you need to bake these cakes right after mixing or else they will fail. Baking powder contains baking soda, along with a cream of tarter or other acidic ingredient. Double acting powders react in two phases – at room temperature and then when heated in the oven. So batters made with this baking powder can stand for a while before baking.