What is the difference between baking soda and baking powder and what is there use in cooking and baking? These questions were answered in the latest Common Formative Assessment (CFA) that our chemistry students took. CFAs are one of the latest tools that our district is requiring we do. Ideally they are supposed to drive education by assessing students learning on topics before testing them to gage their understanding. We used to call these quizzes but in the new age of teaching we have a new acronym. The experts tell us that CFAs should be designed to be shorter than quizzes and may be verbal. However, we have to keep track of the results in a predetermined format is very time consuming. Fortunately Chris Pagliaro, a social studies teacher at SHS, made it easier to keep track. In addition, we are now doing CFAs to assess reading comprehension in all of our classes - CFAs on Steroids! Why do all this? To prove we are teaching of course. If my tone sounds like I do not really care for these, you should hear what my students have to say about them. Enough of my rant about CFAs. Besides, I actually learned something about baking from from developing this latest reading CFA with Tony Ciccone.
The article we used for the reading CFA was from our textbook, Chemistry - Matter and Change, McGraw-Hill 2008. The article, Acid-Base Reactions on the Rise, describes the two questions from the first sentence of this post. Baking soda and baking powder are both considered be leavening agents. A leavening agent is an ingredient that causes batter to rise during cooking or baking. Baking soda is composed of sodium bicarbonate (NaHCO3) which is a base. When mixed with an acid, even a weak acid, reacts to form bubbles of carbon dioxide (CO2). When using baking soda for cooking, it is usually added last to the batter. That is because the other ingredients are often acidic and will produce the carbon dioxide bubbles as soon as the baking soda is added to the batter. Mildly acidic ingredients used in cooking and baking include vinegar, chocolate, honey, lemon juice, milk and many others. Some batters, however, are mildly acidic and, therefore, must be made acidic. This is where baking powder comes in. It turns out baking powder is a mixture of sodium bicarbonate and a dry acid (cream of tartar - potassium bitartrate or acid of calcium phosphate - calcium dihydrogen phosphate) and starch. So that's it!