In a previous post I wrote about my philosophy for teaching nature study to elementary-school kids, and promised to mention the book I'm going to use next year with Oscar. Here it is: Messing Around with Baking Chemistry by Bernie Zubrowski, from the Children's Museum Activity Book series. (Little, Brown, and Co., 1981; ISBN 0-316-98878-2)
There are a lot of books about "kitchen chemistry" out there, and most of them don't really fit my style. This one, however, is a little bit different.
The usual problem with many of these books of demonstrations — I do not call them "experiments" — is that they are all about being impressive, and only superficially treat the deeper reasons why the material works. A particular handicap is that the level of chemistry knowledge which elementary-school-age children might actually be able to assimilate — inorganic solution chemistry — is not readily available in the home kitchen, and most of the solutions that change colors or do otherwise interesting things are, um, toxic. So the kitchen chemistry books play with baking soda and vinegar and call the one a base and the other an acid, and demonstrate that acids and bases combine to give off carbon dioxide. Also that this is how volcanoes work. Um. No.
For good reason, introductory chemistry courses in formal study — high school and college — do not begin with sodium bicarbonate, but instead begin with inorganic hydroxides. Nor do they begin with acetic acid, but instead with inorganic acids. They are simpler systems that readily demonstrate basic principles of stoichiometry. (You try to demonstrate Dalton's law of Multiple Proportions in your kitchen when your reaction evolves a gas.)
Because this tendency in kids' science books irritates me so much, I never thought I'd use one that relies heavily on baking soda and vinegar. Well, I spoke too soon. This one's pretty good.
For one thing, it doesn't pretend to teach the fundamentals of chemistry. Instead, what it's teaching are the fundamentals of laboratory practice: as I wrote in my earlier post, "developing skills of safely handling, carefully observing, accurately describing, faithfully reporting, and logically analyzing." And I think with a little bit of emphasis on my part it can also teach that "we can learn from our experiences and make predictions about the future, and when our predictions are wrong we have still learned something" — this is no less than the fundamental postulate underlying all of natural science.
For another thing, it is honest about its limitations. Zubrowski writes in the introduction, "What this book is about is how to investigate the chemistry of cake and bread making." Indeed, "how to investigate" — not "This book will teach you all about the chemistry of cakes" or "this book will teach you why cakes and bread rise" or "this book will teach fundamental concepts of chemistry."
No, what it does it encourage kids to begin with recipes, change them, and observe the differences in the results. This is different from most of the activities in kids' kitchen chemistry books — it's not just a demonstration ("Drop some food coloring in a jar of warm water and a jar of cold water and see what happens! If you did it right, you'll see that the color spread faster in the warm water!"), it's actually an experiment. If I require the child to keep a laboratory notebook and run parallel experiments with "control" cakes, then he'll really be doing a real experiment — much like my soaked-flour-in-the-bread-machine series I wrote about earlier.
The experiments in cake-baking are followed by activities that demonstrate the effects of mixing various liquids with baking powder, and the author does not commit the error of calling these activities "experiments." He writes, "If you play with baking powder by itself you will find that it does some very curious things…" and suggests that the child keep a record of his observations. To introduce an activity in which the baking powder is mixed with soap water, he writes: "Now here is something special to try that will show you what happens to the baking powder when it is added to the cake batter." The explanation: "The foam, especially in the sudsy water, is similar to what happens in cake batter. The water in the milk in the batter reacts with the baking powder to make small bubbles. In the sudsy water, air is trapped by detergent film. In the cake the combination of flour, eggs, and milk forms a sticky dough that traps the bubbles as they are formed."
Question: What makes things fizzy?
In this experiment, you will produce different combinations of mixtures that react to form fizzy solutions. You'll start with a baking soda/vinegar mixture and then move on to produce your own safe-to-drink, though not particularly tasty, lemon soda.
Science concept: Certain materials, when brought into contact with other materials, react in a way that forms bubbles. Acids and bases often combine to form carbon dioxide, which, as a gas, is what makes carbonated soda fizzy. You'll be experimenting with several common ingredients to determine which react in this way.
The last statement is an out-and-out lie, and the thing about acids and bases "often" combining to form carbon dioxide is… well… misleading at best. Not to mention implying that this is how soda drinks are carbonated. Oh, by the way, one of the "reactions" is dropping a lump of dry ice into some water, which illustrates a physical (not chemical) change.
Back to Zubrowski. Because he has kids making small cakes (6 Tbsp of flour in each one), we can use that to discuss the concept of scale-up. Because he has kids comparing recipes that have been altered by one change at a time, we can discuss experimental design and controls. There are several activities where mixtures of different quantities are compared, so the importance of measurement and careful replication is demonstrated. Different brands of baking powder are compared: since these will, of course, have different prices, there's a nod to economics and to variations in quality control from different suppliers, which Dad-the-process-engineer is really going to appreciate. A suggestion that the child try making a baking soda cake with orange juice leads me to think the child ought to be able to design his own recipe based on what he's learned from the previous experiments.
Gas collection syst
ems begin with crude balloons-on-bottles but progress to the child's building a gas generator and a collection system in which the volume of gas can actually be measured. (Here's where I'm going to go the extra mile and get some lab equipment — no need to bore holes in rubber balls stuck in the necks of jars when I have access to
online retailers that will sell me value-priced two-hole stoppers and Erlenmeyer flasks). The child is encouraged to try several activities that demonstrate the properties of the gas. "Experiments?" No! Zubrowski writes, "Just what is this gas? Is it plain old air or does it have special properties?… One of the jobs of a chemist is to find out about things like this. Scientists have developed all sorts of tests for substances to find out exactly what they are. Here are some you can try." He goes on to tell how the child can demonstrate that the gas doesn't support combustion, is heavier than air — a chance to explain molecular mass! — and dissolves in water to form an acidic solution). And then, rather than claiming that all these tests prove it's carbon dioxide, he warns the reader "You would need to do other tests to establish this fully…" (Guess what. I can buy saturated lime water online. Problem solved.)
Why does the language matter so much to me? It reminds me a little bit about my philosophy towards child discipline. With discipline responses, the most important thing to me isn't whether a given technique, or way of explaining things, "works" (appears to give immediate results). I obviously don't want to choose things that turn out NOT to work, but not just anything that appears to "work" will do. Ultimately, I choose techniques and language that I am comfortable using: language and actions that communicate the truth, namely, that the child is a human person deserving of respect while learning, AND that I as his parent have a real, natural, and just authority over him, AND that I expect him to learn to comport himself more and more as he gains experience and maturity. If I can't find something that meets both those criteria (truth and effectiveness), I'm going to do my best to try to come up with one, and in the meantime I err on the side of truth over apparent effectiveness. Because I believe that the truth IS effective, even if it seems to take longer than, say, duct-taping a kid's mouth shut.
For the same reason, I need to use books that use language I can stand to hear. Language that isn't dumbed down so much that it no longer accurately describes what's physically going on.
So… even though Exploding Color Changing Slime may appear to get kids interested in science, really it only demonstrates that kids are interested in exploding color changing slime. Which is not representative of "science." I'd rather introduce children to what workaday science really means: observation, measurement, recording, communicating, repeating and repeating and repeating, calculating, predicting, testing. It is not, perhaps, as impressive; it perhaps will not produce wide-eyed wonder, at least not right away. But it is true, and I think there is a special kind of quiet fascination that some children can find in the thought: I can do this. I can discover this. I can measure this. I can find it out for myself. It takes longer to develop, but I think it will stick.
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