This could be the most important question for students to be asking in chemistry; “How?” At almost every level of chem, one of the primary goals is to figure out, how did that happen. I use this simple demo and a short video to help students see the importance of asking how. This whole demo, video and discussion only takes about 10 minutes.
The Demo
Have three 150 mL beakers out. Without telling the students, in the back room, place a few drops of phenolphthalein in the first beaker. Put 1-2 drops of sodium hydroxide solution in the second. And then 3-4 drops of equimolar hydrochloric acid in the third.
Once up in front of the kids, I announce that we are going to do a little analysis of our city water. I fill the first beaker with water, swirl it a little, and then ask if it looks cloudy or chunky. It must just have been a dirty beaker, right? I pour the water that now contains phenolphthalein into the second beaker. It turns bright pink with the presence of the sodium hydroxide. There is definitely something in our city water. That doesn’t make any sense. So I pour it into the third beaker and it reacts with the acid to become clear again.
Once the students have seen the demo, I ask them how I did it. Since they don’t know any real chemistry yet, the answers are approximately, “You put something in the water.” And this gives me the chance to ask an important question. How do you know that I put something in the water? What I am trying to have them consider is that they already understand some basic patterns that are expected in nature. Water shouldn’t change color when poured into separate beaker. And since it did, there must be something else present. It’s no duh caliber science. But it may be the first time that you get to expose them to the fact that they are very familiar with the consistency (even use the word periodicity) of the natural world.
The Video
I then show them this short video of The Carbonarro Effect. It is a reality show about a magician that goes undercover and does magic tricks on people while hidden cameras film their response.
The lady in the video is asking a simple question. And the secret magician never answers it. She is asking how. How did the two balls fit in the box? And he is answering her question with the “why”. It is very unsatisfying to the lady. She wants to know how it happened. Just like we should in chemistry.
How did the water turn pink? How did the water turn clear again? How? And through the discussion in class, you can set the expectation that chemistry class is for asking that very question. How did that happen? In order to be able to answer that question, we have to know enough about atoms and their predictable behaviors to see how their interactions would happen like that. Getting students to wonder and ask how is key to their development in chemistry. The demo and the video bring up some simple, but good points about our perspective in the world. We want to know how something happens. And that is what chemistry is for.
Want to engage your students in a new way as you introduce the naming compounds? Try CHeMgO. It’s the instant bingo-style formula writing game with four levels of challenge so it grows with your students. Check it out.
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