Introduction

Students often struggle with remembering that one, crucial visual reference that can help them retain and fully understand key concepts.1 Personal experience indicates this struggle is especially true of high school chemistry students in introductory courses. Teachers can struggle, too, with crafting creative approaches and opportunities that seek to bridge the gap in students’ understanding and capture the image needed for abstract content retention.

Carefully selected chemical demonstrations provide the chance for teachers to display scientific phenomena that foster students’ curiosity and aid in retention of content. Demonstrations also provide an avenue for students to practice and hone essential skills, such as writing in the discipline. In other words, chemical demonstrations serve as means to increase students’ scientific literacy.

Here, we submit a brief but impactful demonstration designed for the beginning of a unit on chemical reactions. Subsequently, the teacher uses the demonstration as a vehicle that drives instruction for the remainder of the unit. As stated in Content Matters,2 to facilitate authentic science learning, “students have to own it, possess it, and use it several times.”

This demonstration also gives students the opportunity to write detailed observations of a chemical event, to use their data to write an experimental procedure about acids, to interact and learn about the activity series of single replacement reactions, and to connect to current events. Further, writing in the discipline is a key component every time the class revisits the demonstration and its phenomena. These activities are an intentional effort to build scientific literacy in the chemistry students, and to structure the curriculum as if students were doing the work of a chemist.

Deliberate development of scientific literacy

Cultivating scientific literacy in students begins with purposeful instances of students engaged in scientific inquiry, the “keystone of DL (disciplinary literacy) science.”3 Further, a curriculum designed around inquiry serves as a platform for students to master core subject matter aligned to state standards. The chemical demonstration will exemplify scientific literacy through students’ “capacity to pose and evaluate arguments based on evidence and to apply conclusions from such arguments appropriately.”4

The demonstration

Figure 1. Outcome of the chemical reactions is shown.

Two test tubes, each with a small amount (~0.1 g) of granulated copper, are clamped to a ring stand inside a fume hood. The teacher, wearing protective safety goggles and lab coat, explains that a different acid will be added to each test tube. About 5 mL of “Acid A” (concentrated hydrochloric acid, HCl) are added to the first test tube. Students record observations in a notebook. Then, about 5 mL of “Acid B” (concentrated nitric acid, HNO3) are added to the second test tube. The concentrated acids are handled with care, and the demonstration is performed in the fume hood due to the emission of noxious fumes from both the acids and subsequent NO2 gas formation.

Students again record observations in their notebooks. The Cu and HCl do not react, and the acid simply rests atop the solid granules. In contrast, the Cu and HNO3 produce a vigorous reaction, with brown NO2 gas billowing out of the test tube and a vivid blue Cu(NO3)2 solution resting at the bottom of the test tube. The differences in the two reactions engages the students in a scientifically-oriented question5: “Why is there is a difference in the results of adding Acid A to the copper versus adding Acid B?”

Rekindling the need to write good observations of science phenomena

Figure 2. Students record and discuss qualitative observations from the demonstration.

Previously during this course, students complete a few lab assignments that require recording detailed observations of reactions — but without the need to use those observations to determine products, or draw specific conclusions. This demonstration gives students the opportunity to hone their observation skills with the expressed purpose of using the observations as evidence later in the unit, a skill at the core of scientific literacy.

Chemists need to collect observations as qualitative data, and use it as evidence to rationalize outcomes of reactions. As “learners give priority to evidence,”6 they are practicing an essential feature of classroom inquiry, which is also a foundational piece of scientific literacy. Further, reading through the observations allows these younger students to elicit the true benefit of performing demonstrations: the vivid memories and visual stimuli of the demonstration.

Practice writing experimental procedures to explain and test science phenomena

Next Generation Science Standards (NGSS) mandate that students assess the design of experiments to explain phenomena in a systematic manner.7 In our curriculum, students do not seemingly have enough opportunities to write about what they observe, and even fewer chances to interpret and transform what they observed to make sense of the experimental design.

Writing in the science discipline is critical, especially on the college level. Writing can be applied to any discipline, and often manifests itself in one of two forms: learning to write, or writing to learn. College courses often focus on the “learning to write” portion: developing and mastering skills necessary to formally disseminate scientific findings.

The lesser utilized, but arguably more important, form is “writing to learn.” Activities, such as the demonstration presented here, provide opportunities for students to explore new topics, translate the information into language they more easily understand, and develop an associated recall mechanism. Teaching students these essential writing skills early on will help them in their understanding of more complex scientific topics encountered later in their academic careers. It provides an alternative, more non-traditional method of learning chemistry, where the focus is taken off of memorizing facts and formulas and is instead placed on rational thought process and explanation of observations.

Platform for rich discussion of content

Activity series of single replacement reactions
The state standards for chemistry in South Carolina include guidance for Chemistry Conceptual Understanding (Standard H.C.6A)8 that necessitates that students use knowledge of the reactants to predict products of chemical reactions.

The demonstration described above provides students a prime opportunity to use the activity series for single replacement reactions to partially explain the demonstration’s outcome. For the first reaction (copper mixed with hydrochloric acid), the activity series provides the explanation for why copper cannot replace hydrogen; however, the most engaged students will recognize discrepant results with regard to the second reaction (copper mixed with nitric acid). The activity series alone cannot provide support for why the second reaction still occurred despite copper’s lower activity relative to hydrogen.

These discrepant results encourage students to “evaluate their explanations in light of alternative explanations”9 in order to understand the overall demonstration. Introduction of upcoming redox concepts helps solidify understanding of the entire demonstration.

Oxidation and reduction
The demonstration cannot be fully explained without the inclusion of oxidation and reduction concepts. As stated, the copper cannot replace the hydrogen ion in nitric acid. However, the copper can react with the nitrate ion in the nitric acid. The copper is oxidized from Cu0 to Cu2+ as the nitrogen in nitrate is reduced from N5+ to N2+ in NO. The NO quickly reacts with O2 to form the brown gaseous NO2.10 This series of redox reactions introduces the students to the rich, new field of redox chemistry, and supplies the best explanation for the phenomena they observed in the initial demonstration.

Figure 3. Students analyze diagrams and record answers to questions corresponding to an article on NO2 gas.

Current events
A broader application of scientific literacy is the student’s ability to apply classroom content to real world problems. Students achieved this when analyzing a recent article11 about the contribution of NOx gases (such as the brown NO2 gas from the demonstration) to smog pollution. Students were presented with the current events article to read critically, as well as several general diagrams that depict the role of NO2 in smog formation. From that material, students “socialize intelligence” when answering question prompts — yet another key principle of learning.12

Conclusion

Structuring curriculum to facilitate and maximize science literacy is a worthwhile endeavor. Implementation of rich classroom activities, such as chemical demonstrations, provides students with an ongoing opportunity to hone their writing skills and meet state content standards.

When students write observations of demonstration phenomena, they are “writing to learn.” When students design an experiment based on such phenomena, they are taking the first steps in “learning to write.” Continually revisiting demonstration phenomena throughout a curriculum allows students to justify scientific principles. Finally, students can apply their learning to current events and issues to demonstrate scientific literacy. If such activities are designed within a careful and deliberate framework, students can absorb material more effectively, and begin authentically learning in the discipline.


References

  1. Kouyoumdjian, H. Learning Through Visuals. Blog on Psychology Today web site, https://www.psychologytoday.com/us/blog/get-psyched/201207/learning-through-visuals (accessed Jan 11, 2019).
  2. McConachie, S.M., Petrosky, A.R. Content Matters: A Disciplinary Literacy Approach to Improving Student Learning. Jossey-Bass: San Francisco, CA, 2010; p 104.
  3. Ibid, p. 94.
  4. National Research Council. National Science Education Standards; The National Academies Press: Washington, D.C., 1996; available at https://www.nap.edu/read/4962/chapter/4 (accessed Dec 12, 2018).
  5. National Research Council, Inquiry and the National Science Education Standards; The National Academies Press: Washington, D.C., 2000; available at https://www.nap.edu/read/9596/chapter/3#25 (accessed Dec 12, 2018).
  6. Ibid.
  7. National Science Teachers Association web page. “Science and Engineering Practices: Constructing Explanations and Designing Solutions,” available at https://ngss.nsta.org/Practices.aspx?id=6 (accessed Dec 12, 2018).
  8. South Carolina Department of Education, “2014 Science Standards,” available at https://ed.sc.gov/instruction/standards-learning/science/standards/ (accessed Dec 12, 2018).
  9. National Research Council, 2000.
  10. University of Minnesota web page, “Nitric Acid Acts Upon Copper,” available at https://chem.umn.edu/nitric-acid-acts-upon-copper, n.d. (accessed Dec 12, 2018).
  11. Gramling, C. Gassy farm soils are a shockingly large source of these air pollutants. Science News, Jan 31, 2018; available at https://www.sciencenews.org/article/gassy-farm-soils-are-shockingly-large-source-these-air-pollutants (accessed Dec 12, 2018).
  12. McConachie and Petrosky, p. 107.