I’ve been using the flame test lab in the wrong unit. Have you? For years, I’ve always used the flame test lab in my grade-level chemistry class in the electron configuration unit. While it does work there, I think it is even more useful in a different unit, history of the atom. Let me explain how using the flame test earlier might help you connect more concepts together for your students.
History of the atom is a hard unit for labs.
I have struggled for years to find an engaging lab that also pushes the curriculum forward in the history unit. Just for context, in the history unit, I teach about the discovery of the atom and the subatomic particles. It ends with being able to relate atomic number, atomic mass, protons neutrons, electrons, and charge. I have a game that I play (that will be released some day on Stoich Decks!) for one block period. I just haven’t found the physical manipulative that I like. Yes, I could model how gold foil experiment works with marbles. But I found that kind of silly.
Flame test allows for macroscopic observations of a microscopic process.
Before we even do the lab, I ask the students to prove that their desks are made of atoms. Most pound on it, saying “If it wasn’t made of atoms, I couldn’t do this.” But then I interrupt their discussions and have their discussion partner refute their argument as if they were Aristotle. Earth. Wind. Fire. Water. They discover that proving their desk is made of atoms is pretty hard since they can’t observe atoms. Doing the flame test allows them to make observations just like the people before science knew about atoms. Why is the copper solution green and the potassium lilac? What could the possibilities be? Having these discussion in groups actually helps them walk their minds through the process that past scientists must have had to walk. The students seem to begin to understand the true challenge that proving atoms, yet alone subatomic particles, really is.
Flame tests help lead into Dalton’s atomic theory.
All atoms of the same element are identical. Those of different elements are different. This seems like “no duh science” to the kids. But doing the flame tests at the same time they are discussing the atomic theory seemed to help. After the lab, I went around the room and had them share what color they saw with copper ions. Everyone said green. Then I was able to go straight into Dalton’s theory. This seemed to help the dryness of atomic theory. They were connecting it to something real.
Flame tests are memorable.
Kids remember sticking things in fire and making color. It’s a neat process. They want to see what colors come next. I also flame test my face. Seriously. At the end of the lab, I will run the inoculating loop on my nose, and since I have been in a room with Bunsen burners all day, I have a good sweat going. Then I have the kids see if they can decide what ion is on my face. The kids think it’s funny, but they also realize that there really is sodium ions coming out of me. They will remember that. Which is perfect, since I will use this phenomenon later when we study electron structure. I will be able to reference back and they will remember the process.
Students can try to solve real problems with flame tests.
I create two unknown mixtures that the students have to try to figure out what ions are involved. It can be really tricky. Pro tip: Never use sodium in your mixtures, the intense yellow washes out any hope of seeing another color. While analyzing the mixture they begin to see how challenging it can be to take a qualitative analysis and apply it to solving a problem. The kids like to argue over what they think they saw in the mixtures. It also helps them understand and have some empathy for the scientists of the past, who really just had these types of observations to make theories about the nature of matter. It’s actually really hard. No, they weren’t dumb because they didn’t understand atoms. They just had a huge challenge in front of them. And now we get to stand on their shoulders. It is a privilege. And some day, someone else will stand on our shoulders, if we attack the world with the same ferocious curiosity.
I had a couple of students stir their curiosity. One girl asked if she could try to figure out what elements were in her makeup by testing it. We tried it and nothing showed up. What about mascara? Tried it too with no results. She was bummed, but got to allow her curiosity to grow. Another student asked if she could flame test her hair. No. I don’t need that smell in my room. But I was able to explain to her what most proteins are made of and have her guess if she would see any of the colors that we got today. Again, I love curiosity.
At the beginning of the year, when the kids sign a lab safety contract, I make them a deal. If they ever wonder something in class, they tell me. What happens when I…? I want them to ask if they can do it. I want them to wonder. I want them to think outside the lab instructions. I want them to wonder about their world. But I also want them safe. So, the deal I make is that they can wonder, but they must also always ask. If I tell them they can do it, then we will do it safely together. And if the answer is no, then the answer is no. It is a freeing activity to do with kids. And yes, kids in the last class asked if we could pour all the chemicals together to see the flame test. Yes, we can. And it’s sodium yellow. Pretty lame. But it was their idea.
My flame test method.
My write-up is pretty simple. It really is just make observations. The setup on this lab is not bad at all. I chose chlorides of lithium, sodium, potassium, magnesium, strontium, and copper (II). I don’t measure how much solid I put in each 50 mL beaker, but it is very small, a tenth of a gram or less. Then I dissolved it with 20 mL of deionized water. I then split that 20 mL into two separate beakers. I ended up with 12 beakers with a small amount of solution that the students could share. I showed them how little we had and how they had to be good stewards. I made it through 70 students and could have done another 70. At each lab station, the kids will need a Bunsen burner, an inoculating loop, and a beaker with some deionized water for rinsing. All the students have to do is get one loopful of the solution and heat it at the edge of the flame. Then they record the color. Rinse the loop, trade beakers with another group, and do it again. Pretty simple. Relatively safe and with minimal waste.
I encourage you to experiment with your experiments. See if there are better places to put labs that allow the students to grow more. I loved using flame tests early. It will be something I repeat. On a separate note, does anyone have a cool lab for the electron configuration lab? I may have just used mine up.
Always looking for new ways to engage your students? Try using games! Stoich Decks has three curriculum-driven games that will become tools in your teaching toolbelt. Use Up & Atom to teach the relationships among moles, grams, and atoms. Use CHeMgO to teach all the way through the ionic formula unit, because the game grows with their skills. Try Trendy in the periodic trend units. Watch kids play a fast-paced game while discussing atomic radius, effective nuclear charge, electronegativity, first ionization energy and electron affinity. The 20% off Pre-order Sale for Trendy is almost over! Try them today!
Comments