Ten to twelve year olds.
Focused on schoolwork for over an hour.
If you are a teacher and reading this, I hope you are sufficiently impressed. For me, this was amazing on an alert-the-media scale.
The funniest part is that the lesson was borne out of my laziness.
So far we haven't done any experiments that explore baking. The possibilities are broad: baking is a chemical process; certain ingredients will make a cake rise; leaving out key ingredients can yield varied results. I have wanted to address some of this, but frankly, trying to figure out how to design an experiment that could be completed in the time we have and that would produce something edible has escaped me.
After reading the other night about what the actual difference is between baking soda and baking powder (something I've never understood or bothered to look into), I went into the kitchen and started messing around with those two substances. Based on my results, I decided we wouldn't do any baking on Friday, but we would test these substances and try to learn more about them using scientific process.
The question I posed was: How are baking soda and baking powder different? We did a quick review of acids and bases and I reminded everyone that the fizzy lemonade produced a chemical reaction because and acid and base were mixed and released a gas as part of their reaction. I introduced the word neutral to define water's relationship to acids and bases. We also reviewed other signs of a chemical reaction (energy release in the form of sound, heat, or light; color change).
I showed everyone the materials we had and how they would test for reactions: I had lemon juice, water and egg whites (which I discovered, thanks to the wonders of Google, are a mild base). They would need to mix each of these liquids first with baking soda, then with baking powder. And for this experiment they would need to record a procedure either before they started or as they worked. Add in recording their own observations and recording a conclusion, and this is the most independent experiment the class has done so far.
I let kids choose their groups with the understanding that if they fooled around, they'd have to re-do the experiment at recess on Monday. Then groups of three and four went off to get organized while I set out all their materials.
Once they had hypotheses written and data tables set up, they were okayed to get their materials and start testing. Some groups recorded their planned procedure before starting; some wrote it out as they tested.
Overall I was amazed to see how well each group worked together and how thoughtful they were as they did their testing. Sometimes working with friends helps with focus, but at other times it can be a hindrance.
In case you are wondering, the baking soda only reacted when mixed with the lemon juice, but the baking powder reacted with all three liquids. As kids moved into writing their conclusions, I reminded them to look back at the question and use their data to answer the question. Most kids correctly identified that the baking powder reacted more than the baking soda. When pressed to guess why, everyone was stumped.
Time for my five minutes of science/kitchen content: The cool thing I found when Googling the two powders is that baking soda is a base, but baking powder is a mixture of a dried base and a dried acid. When it encounters any liquid, a chemical reaction ensues. Which is why whenever I bake a cake or muffins, baking powder is one of the ingredients. We talked about how you could get the desired reaction with baking soda and a mild acid like vinegar or lemon juice if you didn't have baking powder on hand. And I also made sure everyone thought about how the gas bubbles give a baked product that nice lift, evidenced by the little holes you can see when you break it apart. Do brownies need baking powder? Not if you like them fudgy like I do.
Certainly there's a lot more to the role of baking soda and baking powder in the kitchen, more than I am aware of and could explain to my class. Regardless, my students spent a long chunk of time independently using the scientific method to investigate two real-life and common ingredients and draw some conclusions about them.
On Friday afternoon.