There's no doubt about it! Students love chemistry demonstrations. And physics demonstrations. And any science demonstration. And I love them too! Who couldn't love a science demonstration? Science museums stay in business not because there are a bunch of people inside showing PowerPoint slides; and not because there is an opportunity to sit around tables solving stoichiometry or projectile problems; and not because there are booths where you can sit down and balance chemical equations or draw free-body diagrams. Rather, science museums stay in business because there are interesting things to look at, to watch, and to interact with. And when these things happen, people learn. And the learning that does happen is more closely tied to the content which is being learned; it is not abstracted, detached, nor remote.
Students love demonstrations. They enjoy them. But do they learn from them? Now that's a tough question. And an important one. After all, my science class should be about more than just having fun. It should be more than entertainment. If my professional goals centered around providing fun and entertainment for others, then I should have sought to obtain a job at a museum. Or at a zoo. Or in a circus. But my professional aspirations are centered around educating high schoolers and that naturally landed me a job in a high school teaching science.
In addition to a couple of lab experiences, there were three noteworthy demonstrations this week in my chemistry class. On Monday, we were talking about solubility and saturation of solutions. To demonstrate a supersaturated solution, a hunk (new measurement unit) of sodium acetate was placed in a beaker of 10 mL of water. It was heated and heated and eventually dissolved; there's a definite chemistry lesson in this. Then the solution of dissolved NaAc (as it is affectionately known) is poured into a clean buret; it cools over the next 30 minutes as we discuss variables effecting solubility, solubility curves, unsaturated vs. saturated vs. supersaturated solutions, etc. Near the end of class we return to the back of the room. The solution drips from the buret onto a watch glass with a single crystal of NaAc. Students watch in amazement as the dissolved NaAc immediately crystallizes, forming a tall column of undissolved solid. (View picture.) Entertaining? Defintely! Enjoyable? Clearly. Educational? Potentially. For certain, the entire cycle of dissolving the NaAc at high temperatures, allowing for supersaturation through cooling, and ultimately the crystallization of the NaAc as it dripped from the buret was the bridge which connected the content of the lesson to the real world of chemistry. Thanks to the demo, the content was no longer abstracted, detached nor remote; rather, it was alive and happening before their very eyes. Big bang. Big buck.
As a St. Patrick's Day demonstration this past Wednesday, some boric acid was dissolved in methanol, squirted on a lab table in the shape of a shamrock and lit. For 20-30 seconds, a green flame in the shape of a shamrock emerges from the lab table. The green of the flame is a characteristic of boron's emission spectra. Students responded immediately: "Cool" "Wow!" "OMG" "Do it again!" After three more repetitions and about three more minutes, students were back in their seats cranking out molarity calculations. Little bang, little buck. This is a demo that's mostly entertainment. Definitely fun. (And unfortunately it did leave with a lot of leftover boric acid and methanol.)
On a third day this week in chemistry class, I complemented a lesson on molarity and dilution with a demonstration in which two solutions were made by dissolving a known amount of copper chloride in a 200 mL volumetric flask of water. Lab techniques were demonstrated and students calculated the concentrations. One solution was five times the concentration of the other. We noted the color of the two solutions; that was a separate lesson in itself. Then I took out 40 mL of the more concentrated solution and placed it in a third 200 mL volumetric flask; we calculated the moles of copper chloride present in that 40 mL. Then I added water to this 40 mL to fill the flask to the 200 mL mark. As I added the water, I asked students how much copper chloride was I presently adding; they all agreed - none. When finished diluting the solution, I asked students to calculate the concentration. We all agreed that the new concentration was the same as the concentration of the more dilute solution; we noted the color. I discussed the concept of dilution, dilution calculations and a dilution factor. I thought this was big bang. Attachment of content to real world. The dilution concept from the textbook coming alive. A chance to discuss good lab technique. A chance to demonstrate the types of questions which a chemist asks. A chance to see chemistry happen. Entertaining? Not really. Enjoyable? I enjoyed it; my students would rather be watching green flames or see a column of NaAc grow tall. Educational? Potentially.
Why do demos? is the question I am pondering. Why skip demos? is a question which is easy to answer. They take time to prepare. (Planning, practicing and preparing the dilution demo took me close to 50 minutes. Preparing and practicing the NaAc demo took me a half hour.) They take time to clean up and sometimes they are a pain to clean up. (The boric acid is mildly toxic; methanol causes blindness if ingested; and my St. Patricks day demo left me with an extra 200 mL of toxic mess to dispose of.) They cost money (equipment, materials, chemicals). They take class time to perform. Sometimes they don't work as intended and I get embarrassed (but a good humbling isn't always a bad thing). Sometimes its difficult to think of a demo appropriate to the current topic. (The combustion of the methanol with the boric acid doesn't exactly have a solution theme.) And sometimes we believe that the class time spent showing students demonstrations could be put to better use by doing more educational activities, which usually means doing more drill and practice type work. (For certain, in the time it took me to mix two solutions and then dilute one to the concentration of the other, I could have done at least twice as many molarity and dilution problems.) So if Why skip demos? is a question which quickly evokes some valid answers (or at least some appealing answers), then Why do demos?
As I was cleaning up my mess after class on Thursday, my demo a day commitment came under personal scrutiny. Was there any value to what I was doing? Was I getting any bang for my buck? Why was I exhausting myself with demos? I walked back to the office pondering these questions. When I arrived in my office I observed Mrs. S at her desk. Mrs. S is a veteran in the trade of doing demonstrations. Mrs. S is a chemistry teacher in our department who has a reputation among her colleagues and her students for loving demonstrations. Mrs. S is definitely a demo a day teacher. And to her credit, she does her demonstrations with flare (no pun intended). As there should be, there is a sense of entertainment, even theatre, when Mrs. S does chemical demonstrations. This is not to say that there is no learning going on; it is simply to say that the learning occurs in an environment which captivates her lower-level chemistry students. Her students are hooked! What teacher wouldn't want that?
Hoping for some encouragement, I posed the Why do demos? question to Mrs. S. Without hesitation, she gave me what seemed to be 30 answers to the question. Here is her take on the question:
- Demonstrations provide a sort of "visual cement" for a science course; they provide visual reinforcement of the content material.
- Students will most likely remember the material which is demonstrated. When they reminense about your class, they won't be thinking about worksheets, tests, or PowerPoint slides; they will be remembering your demonstrations.
- Demonstrations bring the textbook material to life and provide relevant application of the content.
- Demonstrations address the need to appeal to the varying learning modalites of students. For many students, seeing is believing and seeing is learning.
- Demonstrations provide a avenue for critical thinking as they often naturally lead to the question why does this happen?
- Demonstrations pique student curiosity; students become more invested when their curiosity is piqued.
- Demonstrations provide an interesting diversion amidst an otherwise drab lesson plan, providing students with an interesting chunk to chew.
- Committing oneself to doing demonstrations encourages a teacher to grow professionally as they learn new ways to present and reinforce content material.
- Demonstrations are FUN - for both teachers and students. They create an atmosphere of exciting inquiry within the classroom.
Shortly after having finished her list, Mrs. S began to bolt out of the office towards the prep room to prepare her upcoming rendition of a chemical demonstration. Out of the corner of my eye, I observed her tie-dye lab coat flash by me. I stopped her and asked if she would be interested in my left-over methanol-boric acid solution. As a veteran of the trade, she knew exactly what it was for. She gladly accepted my offer. And I was quite relieved to have pawned it off on her. Whew! What a relief.
The rest of my lunch period and prep period was busy as I prepared for my afternoon physics sections. I had little time to continue my ponderings until 5 minutes into my first afternoon physics class; the fire alarms sounded and the whole school was evacuated. This gave me a few more minutes of further ponderings on the topic of why do demos? As is usually the case, the fire alarm was a false call and we returned to our classed to finish the school day.
On my 30-minute trek home from school, my car ride thoughts returned to why do demos? I began to think about all those former students, who when reminsicsing about their experience in my course, would inevitably make a comment pertaining to demonstrations. I've never heard such a student make comments like "I remember that one PowerPoint presentation on inertia" or "Have you designed anymore cool worksheets for your students to do" or "Do you still use that one Powerpoint presentation on ..." No! Never! This is not what my former students remember. The record is clear; they make comments like "I still remember that one demonstration when you made the aluminum rod make a sound by stroking it with your hand" or "Have you come up with any new demonstrations to show your students" or "Do you still do that demonstration when you shoot the falling monkey with your projectile launcher?" Students remember my demonstrations and your demonstrations for a reason. Demonstrations are meaningful; they stick in their heads. Demonstrations are visual; they can't forget them. Demonstrations are engaging; they hook kids attention. Demonstrations provide the connection between the concepts we are talking about and the material world which those concepts seek to describe.
Demonstrations are probably the closest thing in our profession to edutainment. They are an engaging and (at times) entertaining means of educating our students. And they are an educational means of entertaining our students. When a professional teacher transparently embeds a demonstration with the lesson content, students become engaged in the lesson. Student investment in the lesson rises and And when the demonstration is presented using effective pedagogical strategies, higher rates of learning inevitably results. A lesson immersed with showing students the operations of the material world is a lesson students will remember. Now what teacher wouldn't want that?
I got an email from Mrs. S the next morning: "By the way, one more reason to do demonstrations: total school evacuation." Now I am really glad I pawned the methanol-boric acid solution off on Mrs. S. Better her than me.
