May 2020 | Resource Feature
Molecules that Changed the World: A Molecular Modeling Project
By Lindsay Davis
In my experience, one of the most challenging topics in chemistry for students is VSEPR theory. Not only do students need to memorize lots of shape names and bond angles, but they are also required to think spatially, imagining that the molecules they are studying can spin and rotate in three-dimensional (3D) space.
I teach the topics of Lewis structures and VSEPR shapes right after I finish atomic theory and periodicity — specifically, the period trend of electronegativity. However, because VSEPR shapes appear so early in my curriculum, some of my standard level students are at a place in their mathematics learning where they have not yet heard of the z-axis, the axis that creates 3D space.
So, not only do I have to teach them chemistry, I may also
have to explain this mathematical principle to them. This kind of abstract
learning can be thought-provoking for some — but puzzling for others. In
addition, many students ask why they need to know about the shapes of molecules
at all, since they will never be able to see this occur in real life in the
|Figure 1. Student model of carbonic acid.
Real-world connections are a major part of my chemistry class. I am a firm believer that students need to learn and see how what we teach connects to their lives. As a culminating project to my Shapes of Molecules unit, I have students select a molecule that “changed the world” from an approved list. Even the most challenging ones can be completed by a student who really understands chemistry at an in-depth level.
My students have never asked to select a molecule that was not on the approved list. However, if a student had a passion for a particular molecule, and was capable of creating its 3D model, I would absolutely allow them to do it.
Each molecule on the list is one that students encounter in the real world, and they are asked to research their chosen molecule’s uses, physical and chemical properties and structure, synthesis reaction, by-products, environmental issues, current events, and more. I also have students build a 3D model of their molecule (see Figures 1 and 2) using any materials they like (except food). They have to affix their model to a base, and then decorate and design it with pictures and objects that describe the molecule’s uses. Then students present their model and accompanying research in a 7–10 minute oral presentation in class.
I have found that this project has become a tradition at my school. Even before a student takes chemistry, she has already seen older students’ projects carried through the hallways and displayed in our art gallery. I also keep my previous-year students’ projects in my classroom until a few weeks before the current students’ projects are due. Students enter chemistry on the first day of school and see these molecule projects scattered around my room. It is one of the first things that they really want to talk about. I hear comments like, “When do we get to make our molecule?” or “I know exactly the kind of molecule I want to do, and I have some great ideas for it already!”
As the year continues, students get involved in other chemistry units … but the molecule project is never far from their thoughts. When it finally comes time to start the Shapes of Molecules unit, they are super excited.
On the first day of the unit, to build hype before introducing the project, I enthusiastically go through a PowerPoint presentation with each class, highlighting some compounds that, indeed, changed the world, such as: penicillin, sodium chloride, potassium nitrate, aspirin, sodium stearate, rubber, and morphine. These substances are not among the approved molecules that students can choose. I just use them as examples, since they are common in everyday life. I find that getting students excited about the learning is the best way to begin, rather than starting with the project assignment, requirements, grading, etc.
The students primarily work on their projects outside of class, so I usually give them about three to four weeks to complete it. They can work individually or with a group of no more than three students. Although students may (and should) work on the project throughout the allotted time, the project is a culmination of the whole unit. Teachers can choose to have deadlines throughout the three-to-four-week period, although I do not. Instead, I give my students multiple reminders on the specific parts of the project they are able to complete as they learn more and more throughout the unit.
After I finish the PowerPoint presentation, I hand out the project assignment and go through the details with the students. There are three main parts to the project:
- Building the 3D model with decorated base
- Researching about the molecule in the real world and creating a PowerPoint or Prezi presentation
- Preparing a 7–10 minute oral presentation in class to explain their research and show their model
Next, I explain my approved list of molecules. The list ranges in level of difficulty. To avoid making a student feel badly about their chemistry ability, I make sure that students know it’s their choice to select their preferred level of challenge, and that there is no extra credit for doing one of the harder molecules; it’s all about internal motivation.
Students always surprise me. Sometimes it is a standard-level student who picks the more challenging molecule because they find it interesting or they want to push themselves, and other times it is a top honors-level student who picks one of the easiest molecules. Here is the approved list of molecules:
Carbon Dioxide, CO2
Carbon Disulfide, CS2
Carbon Tetrachloride, CCl4
Dihydrogen Sulfide, H2S
Hydrogen Peroxide, H2O2
Hypochlorus Acid, HOCl
Nitrous Oxide, N2O
Carbonic Acid, H2CO3
Nitric Acid, HNO3
Nitrogen Dioxide, NO2 Sulfuric Acid, H2SO4
Acetic Acid, CH 3COOH
|Table 1. The approved list of molecules for the project, organized by difficulty level.
After students select their molecules, we start on the conceptual learning that takes a couple of weeks: ionic vs. covalent bonding, valence electrons, Lewis structures, and finally VSEPR theory and polarity. Throughout these weeks, students are able to work more and more on different aspects of their project. The project is due a week or so after finishing the concepts of VSEPR and polarity. For example, if a student selected ammonia, she could start by researching its industrial and consumer uses, molecular properties (like boiling point, density, reactivity, etc.), synthesis reaction, environmental implications, and current event.
After a student learns about Lewis structures, VSEPR shapes,
and polarity in class, she could start to complete that portion of the project
for the PowerPoint slides. She could also then start to make her 3D model of
Once all of the project components are complete, I have
students create an introduction to their oral presentation. Instead of starting
right in with their PowerPoint presentation, some students (with my permission)
choose to make and show a video, put on a skit, or even bring in a food item containing
or representing their molecule.
To download additional resources related to this project, including a student project handout and grading rubric, click here. Please note that in the accompanying classroom resource, although I list the appropriate NGSS standards, I work in an independent school that is neither required to follow these standards nor give any standardized tests.
|Figure 2. Student model of acetylene.
Some teachers may worry about students copying from the projects that are currently on display. In my 10+ years of doing this project, I have never had a student or group copy directly from another project, but sometimes they get some inspiration and apply it to their project. I’m okay with that, because more times than not, what actually happens is that students want to outdo each other, making bigger, more creative, and better projects than the ones they see in my classroom. This year, I had to institute a size limit on the 3D model, because students kept making theirs bigger and bigger.
Something I haven’t yet done in this project is a peer critique. I would like to have students use the rubric that I created to evaluate their peers’ projects. Receiving feedback is so important for growth and learning opportunities. Once students get advice and suggestions from their peers, they should have the opportunity to make changes to their presentation and resubmit it to the teacher for final grading.
After completing this project, I find that students have learned so much about the molecules they encounter in the real world — molecules that they never knew were in foods that they eat or products that they use. My students love being part of the molecule project tradition and seeing their hard work displayed in my classroom for the entire year. This project truly connects with students and helps them to see how chemistry can relate to their own lives and the real world.