One of my clever students wrote this on a whiteboard my first year of teaching. It was a classic “ha ha, hmmm…” moment.
I love the creativity, but that’s not really how you want your students to feel about chemistry! I bet a lot of students could empathize with this whiteboard. So how do we take the mystery out of chemistry?
I think the biggest “mystery” of chemistry is “how do we know?” How did scientists figure out what particles that are too small to see look and behave like? Early chemists like Dalton, Thomson and Rutherford often get passed over in chapter 1 of a textbook. They provide some interesting trivia questions, but nothing more. It seems like the best way for students to understand tiny particles is to observe them the same way Dalton, Thomson and Rutherford did. Enter Modeling Instruction.
I will be posting a series of entries throughout the school year under this title summarizing how the model of chemistry evolves in my class throughout the year. My curriculum ia based on AMTA’s Modeling Instruction curriculum with some tweaks.
The first topic of this series is “underpinnings.” Underpinnings are all the skills necessary to study chemistry that are not necessarily related to chemistry content. This includes the nature of science, calculating slope, stating scientific relationships, sig figs, and unit conversions. You can check out my 180 blog for specific activities I do to address these topics. For now, I want to discuss just the nature of science.
The nature of science is often taught at the beginning of the school year and then ignored for the rest of the year. The beauty of Modeling Instruction is that the nature of science is a thread that is woven throughout the curriculum. For students to really appreciate that thread and understand the model of chemistry, you need to establish the nature of science well at the beginning of the year. Specifically, you need to address the idea of building a scientific model.
The model of chemistry started with an observation. That observation combined with an inference became the first model of a tiny particle. Eventually an observation was made that did not fit that model, so the model had to be amended with the new observation and a new inference. Eventually an observation was made that did not fit the new model and the model had to be amended again. And on and on it goes as better technology leads to better observations. This is the story of science. This is the idea I come back to over and over again throughout the year. Even our current model of chemistry is only the model so far.
I teach this idea of “model building” using the wax block activity (see 180 blog). I love this activity because it is both a discrepant event and a black box. Students make an observation and combine that with an inference to describe how the block words. When they are given flashlights (new technology), their observations may not fit their previous models. That is okay, models can change. When the students are given laser pointers (even newer technology), their models might change again. When the students collaborate with other students, their models might even change again! Of course (to the students’ dismay), there is no answer key for science. All you have is your evidence-based model (so far).
EDIT: I have gotten a lot of questions about the wax block activity over the last year! I wanted to offer some answers to everyone in case you have the same questions. I make these myself buy you can find instructions from Flinn here. You can buy parafin blocks at your grocery store with the pickling supplies. I also put together a script I use that loosely outlines how I structure the activity here. Here are some pro tips as well:
- Make sure the foil is smaller than the blocks. Inspect the sides of the blocks carefully to make sure you cannot see any foil. Students will get curious if they see something and scratch away the wax on the side of the block.
- If you need to break the block apart to redo it, just smack the side of it on the countertop a few times, it should come right apart. With that said, at least one of your blocks will get dropped and it will break open during class. Be on high alert so you can swoop in before the magic is ruined!
- Don’t let your students get away with an easy answer. They will likely draw you a picture of “something” inside the block but not elaborate. This is a good opportunity for students to make more observations and then infer what that “something” could be. Given them a flashlight, put the block on top of objects of different colors, etc.
- Don’t tell them the answer. This is the hardest part! Students get so excited about this activity and at the end all they want to know is “was I right?” This is a perfect opportunity to start building your classroom culture. It’s not just about being right! These wax blocks will come back to haunt you for the remainder of the school year but stay strong!
This is one of my favorite activities of the year. Students ask me about it until the last day of school. Let me know how it goes for you and feel free to message me with any questions!
This theme will come back again and again. My goal for this year is to get my students to truly understand what a model is and how having a model helps us to build a problem-solving framework. I foresee the question, “what’s your model” being asked frequently this year.
Next up in the series: Democritus and his tiny particles