In the culinary world, it is a commonly accepted truth that "cooking is an art but baking is a science." Knowing the differences between salt and baking soda helps your child understand the importance of accuracy and attention to precise details when baking. The chemical functions of each ingredient work together in a delicate balance that determines whether your baker-in-training's end product is a yummy treat or a culinary disaster.
The table salt your child uses in baking is a natural mineral, also called sodium chloride (NaCl). It is an ionic compound, meaning that it includes "equal numbers of positively charged sodium and negatively charged chloride ions," according to the Maldon Salt Company. It forms cube-shaped crystals, so show your child a small wooden block or sugar cube to help him visualize the microscopic salt crystals. If you have a microscope handy, he can examine the salt crystals' shape under magnification. The scientific designation for baking soda is sodium bicarbonate or NaHCO3. This weak base is made up of one molecule each of sodium, hydrogen and carbon and three of oxygen. When combined with cream of tartar, a weak acid, it forms baking powder.
Baking soda is a leavening agent which causes baked goods to rise when your child mixes it with acids such as citrus juices, buttermilk, vinegar, molasses, honey, cream of tartar and chocolate. The expansion effect remains inactive until combined with water or acid, which releases carbon dioxide (CO2) and forms bubbles in the dough that cause it to rise. This is what gives your child's baked goods a light, fluffy texture. Without the bubbles, your child's baked goods will fall flat. Therefore, the University of Nevada Cooperative Extension warns against reducing or eliminating baking soda without using another leavening agent. On the flip side, adding extra baking soda will cause over-rising, which pops the CO2 bubbles, likewise resulting in flat breads and pastries. Along with their different properties, baking soda and salt have very different tastes. Have your child taste a tiny bit of each to highlight the difference.
Salt has several functions in baking. As a flavor enhancer, it helps mask bitter flavors and bring out the sweetness in the sweeteners by contrast. When it interacts with the amino acids in the flour, it toughens up soft fats and sugar by tightening the gluten formation which strengthens the dough's texture and elasticity, explains King Arthur Flour's Professional Baker's Reference Guide. The salt also slows the leavening or rising process to prevent the bread or pastry from rising too quickly, which would cause its shape and flavor to suffer. If you are making bread, too much salt can kill the yeast, leaving you with a flat, hard brick instead of a soft loaf.
Nothing will show your kids the difference between salt and baking soda like hands-on experimentation will. Choose a fairly simply recipe, such as a favorite cookie, biscuit or muffin recipe, which contains both baking soda and salt. Let your child make up several quarter batches, leaving the salt and/or baking soda out of some and reducing or increasing it in others. Label each one with the proportions of these two ingredients used. Bake and compare the appearance, texture and taste of each result. Guide your child to an understanding that the best results in baking come from precision in reading the recipe and measuring accurately to get the exact chemical balance necessary to produce a delicious treat as a reward for his work.