Chemistry Solutions

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As a high school chemistry teacher of 23 years, I have always seen growth in my students over a typical school year, generally through the results of modeling, whiteboard presentations, and written revisions to misconceptions. I also often see my students improving their ability to create and complete experiments independently.

However, I didn’t always feel that my students themselves were seeing their development, or recognizing the importance of reflecting on their learning. To address this disparity, I have implemented a strategy that fosters an ongoing learning process, a strategy from which both the students and I are benefiting.

Searching for a better way

Years ago, I realized that I was not sharing my observations of my students’ growth with them in a tangible way, other than occasionally saying something like, “great job.” I was not giving students a way to reflect on their intellectual development. Indeed, I remember reading an interesting observation about the importance of such input to students. “Independent practice can play an important role in developing self-regulation and metacognition,” I read in the Metacognition and Self-Regulated Learning Report, “provided that tasks are sufficiently challenging, build on firm pupil subject knowledge, are realistic, and are suitably guided and supported by the teacher.”¹ 

After some reflection, I decided I wanted to find a method to help students understand and appreciate how their thinking was being affected.

At the beginning of the year, my students have limited chemistry knowledge, understandably. I post their (often low) pre-test results in their online gradebook (but do not include those results in the semester grade). This score helps establish a baseline for students. Later, at the end of the year, the students re-test and I once again post their scores, which tend to be much-improved since their pre-test. Sadly, however, I’ve noticed that most students are exhausted with school by this time, and therefore do not take pride in their impressive growth.

So, to make their progress more meaningful to them, I now begin the school year by coupling the pre-testing with a set of four example labs that I introduce and then revisit after each unit. These lab examples remain on permanent display in my classroom throughout the school year. To further engage students with these four lab examples, I tell them that they are included as part of the lab portion of their year-end final exam. Using a composition book, students continuously update and modify their understanding of these lab examples throughout the year.

The lab examples

• Saltwater Solutions: Students make qualitative and quantitative observations regarding classification of matter, solubility, dissociation, vaporization, physical properties, and density. I have students fill three 2000mL beakers with water and varying amounts of salt (see Figure 1). Then they place a golf ball in each beaker. Students will see that the golf ball is floating in beaker A; the golf ball is suspended in the middle of the water in beaker B; and the golf ball has sunk to the bottom of beaker C. About halfway through the year, the solutions must be remade, because the water will evaporate. 

Figure 1. Three saltwater solutions of different concentrations, each containing a golf ball.

• Sealed Syringes: Students make observations regarding pressure, volume, temperature, the composition of air, and particle diagrams. They will also graph the relationship between the variables. The end of these syringes have been melted so that a closed system is created. Students push the plunger in and then release while observing the outcome (see Figure 2).
• Single Displacement Reaction: Students make observations about the reactants and products of a chemical reaction between copper and silver nitrate. I use this lab example to help students understand the proof of a chemical reaction, oxidation and reduction of metals, and chemical equations. The first test tube contains a coiled copper wire, the second contains silver nitrate, and third is where the full reaction takes place to show the final products (see Figure 3).

Figure 2. Sealed syringes used in a lab example (left).  Figure 3. Test tubes show the reaction of copper and silver nitrate. (right)

• Investigating Substances: I begin by placing small samples of acetone and water on each lab table, along with a small pile of salt (see Figure 4). Students touch and move each of the three substances with a finger. Throughout the year, they will make additional observations about the substances’ appearance, evaporation, intermolecular attractions, odors, state of matter, and temperature. In my role as teacher, I’m careful to emphasize that students should not mix the substances, since the lab is about each chemical’s individual properties. However, if they do mix them after observations are noted, they’ll see that no reaction occurs — and that can lead to more discussion.

Exploring the labs

Students work with their lab partners to record observations and attempt to explain each lab example in their composition notebook. When they have completed their notes for all four, I make sure to point out that by the end of the school year, they should be able to provide at least 100 observations for all the lab examples! Usually, students are shocked by this statement, since they typically have around 20 observations documented for all four lab examples on their first try — so increasing that total to 100 is big jump. I assure them that, throughout the year, they will continuously increase their understanding of each of these lab examples. The Metacognition and Self-Regulated Learning Report, referenced above, supports this strategy, and highlights the importance of metacognition: “Our pupils need to be able to balance short term goals ...with longer term learning goals and rewards.”

Students recognize this growth as they compile their notes over the year. On the first day of school, students set up their composition books with periodic tables and reference sheets, and three pages designated for each of the four activities. Students glue or tape these sheets into their lab composition books as shown in Figure 5.

When students first investigate the lab examples, their understanding is quite basic. For example, when considering the Sealed Syringes lab example, students usually cannot yet explain “gas pressure,” and often incorrectly say “oxygen” when they mean “air.” But, just a few weeks later, when the gas law unit has been completed, they should have a much clearer understanding. I have students use this moment of insight to reflect on their original thoughts and how their ideas changed, and to correct their original notes. Their understanding continues to evolve as we discuss inverse vs. direct relationships, closed and open systems, variables and constants, and behavior of gases in chemical reactions.

• I chose to use these four lab examples in this way because together, they cover most of the major topics for the entire course:
• Saltwater Solutions: solubility, dissociation, physical properties, vaporization, density, classification of matter, dissolving
• Sealed Syringes: gas laws, graphing, particle diagrams
• Single Displacement Reaction: chemical change, types of chemical reactions, predicting products, balancing equations, ionic equations, nomenclature, mole/mole ratios
• Investigating Substances: states of matter, intermolecular forces, energy transfers, chemical bonding, classification of matter

I have found that this approach offers several advantages. Having students revisit the labs provides a tangible reminder of their learning progression. It also lets students actively participate in revising misconceptions, fostering deeper understanding. The composition notebooks serve as valuable study resources for both regular assessments and final exams. Finally, the method is adaptable to various academic levels and lab preferences.

Correcting misconceptions

Each of the four lab examples can reveal a variety of student misconceptions. As students become aware of their misunderstanding, they update their composition books. To help them recognize when they have a misunderstanding, I try to question their ideas, without giving them a “right” answer. When a topic arises during the year that is connected to a lab example, we discuss it and I also give students time to compare their notes with others. A few common misconceptions I see related to the lab examples include:

• Saltwater Solutions: Saltwater is a liquid; dissolving means disappearing; salt is becoming a liquid when dissolving; salt is chemically changed; and sodium and salt mean the same thing.
• Sealed Syringes: Syringes are filled with oxygen; nitrogen and oxygen are bonded together; pressure is the same as gravity; pressure can’t be felt; and particles have a higher temperature because they are moving faster.
• Single Displacement Reaction: Copper is rusting; this cannot be oxidation since there is no oxygen present; the silver-colored product is rusty copper; and there was not a chemical change because you still have a solid and a liquid present.
• Investigating Substances: All three samples are at different temperatures because the acetone feels colder; salt will take weeks to evaporate; water will take days to evaporate; and acetone is an acid.

As we complete a unit, I have the students go back and look at their notes for each of the four lab examples. Can we add anything new? Students are encouraged to “cross out” earlier misconceptions and add correct answers. I emphasize “crossing out” as opposed to erasing, because I find that students who erase their wrong answers seem to repeat them later. For example, if a student had originally written, “saltwater is a liquid,” and then decides to cross out “liquid” to instead use “aqueous solution,” they may remember the earlier discussion of why that is wrong when reviewing their notes. Figure 6 highlights some examples of the progression of student notes.

Throughout the year, as we revisit the lab examples, students work collaboratively in groups to brainstorm new ideas on whiteboards, while also recalling what they already know (see Figure 7). Each time they do this is a fantastic opportunity to review prior knowledge and continue to address any misconceptions. One already-mentioned misconception that lingers all year is from the Saltwater Solutions lab example: the idea that “saltwater is a liquid.” When we reach the topic of chemical reactions, it is common for students to describe each chemical dropper bottle as containing liquid. I use this as opportunity to question them, and students will laugh and say: Oh! No, it’s an aqueous solution! Another sign of improvement is when I hear students at lab tables correcting each other on common misconceptions. It is a joy to see their confidence and knowledge base improving through this collaborative work. As the authors of a recently-published book on this topic note, “The most relevant repertoires for developing metacognitive skills are learning talk and teaching talk. Learning talk includes narrating, questioning, and discussing; teaching talk includes instruction, exposition, and dialogue.”¹ 

I see collaborative lab work as being similar to the chemical industry, in which a chemist will work with a team to generate viable solutions to a problem. So, as we begin the second half of the year, I limit the number of questions a group can ask me during a lab; this forces the students to work with their fellow group members. Since we do approximately 40 lab activities over the course of the year, it’s important that they apply their developing skills to new labs, reflecting on previous knowledge, using their notes, and collaborating with fellow students.

Reflecting on the process

The lab-based final exam I give at the end of the year may seem time-consuming to grade, but it is not. I simply give a check mark for each correct comment, key word, example, unit, etc. (see Figure 8). As part of the final exam, I add a fifth lab example to challenge students to apply their knowledge to a new, unfamiliar situation.

Any of these lab examples can be changed to match your preferences and the academic level of the students. I’ve found that these labs work well with my general chemistry students, who begin chemistry with little background knowledge. Since these lab examples are very inexpensive to keep set up, I can keep all four activities on display in my classroom so that students see them every day!

I think an important advantage of these activities is that they can give a teacher valuable insights into their students’ misconceptions. In my experience, using this strategy has enhanced student self-awareness, promoted active participation in revising misconceptions, encouraged meaningful notetaking, and created a valuable study tool — all of which contribute to a more positive and successful learning experience. My students’ grades have improved, but more than that, the students are taking on much more responsibility for their own learning, articulating their thoughts with each other in lab groups, and recognizing the importance of metacognitive reflection.

References 

¹ Quigley, A.; Muijs, D.; Stringer, E. C. “Metacognition and self-regulation learning.” London Education Endowment Foundation. Available from: https://educationendowmentfoundation.org.uk/education-evidence/guidance-reports/metacognition (accessed Aug 27, 2024).