September 2023 | Resource Feature
Developing Chemistry Lessons with Student Interest in Mind
By Patricia DeCoster
Making chemistry relevant and enjoyable for my urban high school students has always been a struggle. Except for those students in AP courses, few of my students benefit directly from learning about stoichiometry, balancing equations, or calculating the average mass of isotopes. These and many other concepts are important for college level work, but they provide significant barriers to low-performing and even average high school students.
However, striving for greater relevancy does not mean you need to eliminate rigor. After all, we discuss many complex concepts not taught in “traditional” chemistry courses. Students understand these concepts because they can connect them to their life experiences.
In my school, chemistry classes have been under-enrolled due to a combination of low reading and math skills among most of the school’s population, which prohibited many students from taking chemistry at all. During Covid, I was forced to teach out of my kitchen, bathroom, and garage, which led me to take an entirely different, and more interesting, approach for development of lessons. I set out to design practical lessons that incorporated NGSS standards, based on the needs and experiences of my students. These topics included cooking, medicine, cars, climate change, plastics, and cell phones. I searched for and sometimes developed hands-on lab experiences, as well as projects that would allow students to explore these areas of interest while strengthening their skills in reading, writing, and mathematics.
Over the course of two years, I used student interest surveys and collaborated with teachers within our department to develop the curricula for each topic. In this article, I’d like to share some of these ideas for teachers who are looking to make similar changes in their own classrooms.
Connecting chemistry through essential questions and phenomena
|Figure 1. This photo shows how viscosity is measured for various grades of new motor oil by dropping a ball bearing at the same time in test tubes and measuring the time it takes for them to descend to the bottom. Used motor oil, as described in the article, is not shown here. © Image used with permission of Synlube.com|
One of my strategies was to use a storyline that started with a phenomenon familiar to most students, but that is based on complex chemistry. For instance, “Why do you need to change the oil in your car?” was an essential question used for teaching the topic of cars and organic chemistry. By explaining that oil is necessary for lubricating moving parts in an engine and discussing how an engine can stop working or “seize” if it is not oiled, I connected the chemistry of molecular structure and shape to functionality. The difference in viscosity of various types of motor oil can be demonstrated by dropping a ball bearing in a test tube and measuring the amount of time it takes for the ball to reach the bottom (see Figure 1).
This demonstration connected students’ understanding of molecular shape and intermolecular bonding to the physical properties of a substance. Describing physical properties such as viscosity, color and texture can be difficult for my students, because they lack some basic vocabulary needed to accurately describe their observations. To help them develop some of this vocabulary, I placed a number of possible descriptive words on the board, from which students could choose the ones they wanted to use. Words that describe color, transparency (such as opaque or translucent), particulate matter, etc. were given as choices.
Each student was then encouraged to use their science journals to write at least three questions regarding their observations. For example, students asked, “Why did the ball fall faster through the used oil rather than the new motor oil?” Many students were surprised that used motor oil is less viscous than new motor oil.
I used long and short pieces of wire as models to show students that molecular structure affects properties and function. Soon they discovered that rolling their fingers over shorter pieces was easier, representing the less viscous, shorter polymer chains found in used motor oil.
Students then modified the experiment so that they could better understand what happens in an actual car engine. Some students suggested that we heat the oil; some wanted to see what would happen with different types of oil; and others wanted to see if the oil in the crank case was the same as in the oil pan itself. One student had the ingenious idea of testing the used oil from “old” vs. “new” cars after being driven the same number of miles since the last oil change, to see if the age of a car increased the likelihood of particulate matter in the oil. These discussions led to greater understandings of density, molecular structure and shape, covalent bonding, and even molecular motion.
Explanations and conceptual understanding
Exploring the physical properties of oil and their effect on its function left students with a lot of new questions related to cars. They were curious about how an engine works and the purpose of gasoline inside it. So, using the SE instructional model, my next step as instructor was directed by these questions, even though the unifying theme continued to be the structure and properties of matter (NGSS HS-PS-1). Almost any question related to how engines work will lead you back to this standard.
Next, I introduced the topics of internal combustion engines, gas pressure laws, and kinetic molecular theory. We started by viewing the video, Internal Combustion Engines, from AACT. Students learned about the gas laws, combustion reactions, thermodynamics, and how bonds break and form to release and store energy. This learning was driven by both direct instruction and group activities such as jigsaw and puzzle solving. We also investigated the energy outputs of different types of gasoline, diesel, and jet fuel, after learning how crude oil is separated using fractional distillation through the activity, Investigating Crude Oil. Then, a demonstration of the fractional distillation of Cherry Coke gave students the opportunity to taste, smell, and see how different each fraction is compared to the original mixture. Students were assessed using their science journals, lab reports, participation in group activities, and short formative quizzes administered through Google Classroom.
Through this series of lessons, students now understood the process by which products such as motor oil are produced, as well how running an engine breaks down motor oil into smaller molecules that have different physical properties. As a result, we were able to consider a new essential question, “How does gasoline power our cars?”, which allowed us to investigate how gasoline and other fossil fuels are burned for energy.
I used a standard calorimetry lab that involved burning foods such as Cheetos and potato chips to demonstrate how combustion reactions are linked to the specific heat of water and measuring energy changes. Thermodynamics can be a tricky concept, so we also explored hot and cold packs, which students made themselves. We also investigated how heat and temperature changes are related, yet not the same. I also introduced the concept of entropy, not as an equation, but rather using the second law of thermodynamics and various models, such as building a house of cards or setting up dominoes. There is an excellent TedEd video on entropy called “What triggers a chemical reaction?”, by Kareem Jarrah, which I have used to tie together this part of the unit.
Students also learned that the longer the carbon chain in simple alkanes, the higher the energy output per molecule. We discussed how different types of fossil fuels are “cracked” to make various types of products, and delved into the markets of oil and gas by looking at the prices for these commodities over the last 100 years in relation to geopolitical events. Students researched these periods of time working in small groups, and reported to one another on how prices have fluctuated depending on supply and demand (actual and perceived). This research was presented using Google Slides and a large timeline in our hallway. Economics is an important part of understanding how connections among science, society and technology affect students’ lives. It is important for students to understand that material prices often determine how technology is utilized and by whom.
This insight led to an important discussion about climate change and how fracking and alternative forms of energy such as wind, solar, and nuclear are changing our carbon “footprint.” I used a jigsaw activity to explore this topic, tasking small groups of students with different forms of energy (including gas/diesel). Each group received a short reading packet and WebQuest link; later, students informed each other about the pros and cons of each form of energy in commercial use. Students were broken into small groups to explore the energy inputs and outputs for various types of cars including conventional (gas), hybrid, and electric. I also designed an argumentation lesson that took about four days to complete, but that gave students a good understanding of the complexity of making our transition to a “green” economy in the future. Students presented their findings to the class in person or through video format. Thus, we took thermodynamics beyond the Gibbs Equation, and applied it to real situations that are occurring in real time.
Reinforcing reading and math within the content
While integrating content that appeals to student interest, I also used several different resources to improve their reading skills, including two ChemMatters articles, “Geothermal Power: Hot Stuff” and “Questions from the Classroom: If I buy a more expensive high-octane gasoline, will my car run better?”. I also used the news service, NewsELA to let students read news articles about fossil fuels and answer questions that matched their reading level, including the article, “Where Fossil Fuels Come From” (a license is required for article access).
To increase vocabulary and fluency, we regularly scheduled close readings, where students heard me read, which helped them increase their confidence in pronunciation and pacing of complex texts. The use of graphic organizers such as the Frayer model and thinking maps, as well as word walls, have also helped students understand concepts.
I also gave students a number (usually ten or less) vocabulary words and asked them to make a “jigsaw” puzzle out of them by connecting the nouns with verbs that described related processes. As a result, students were better able to get the conceptual picture of how thermodynamics and kinetic molecular theory explain why certain reactions occur. An excellent article on various reading strategies is in “Strategies for Teaching Science Content Reading,” by Patrick Croner from The Science Education Review.
To develop our math skills, students had to calculate relative viscosity and density, and also used gas laws to predict pressure based on volume changes in a cylinder and temperature changes. I used the Gas Properties PhET simulation and Khan Academy extensively to demonstrate gas laws and energy changes, and to build basic math skills. Most of my students tested at a 4-6 grade level for math skills, so we concentrated on areas of fractions, percentages, graphing (line), and unit conversion. Math was also utilized in the discussion of the concepts of work, efficiency, and mechanical advantage. Since I have several ELL and SPED students, I needed to modify a number of assignments based on ability and IEP requirements. Fortunately, I team-taught with a special education teacher, and we were able to work together to provide the individual support needed during some difficult parts.
Making chemistry “real”
Teaching organically, without a textbook, can be rather difficult — but it does allow you to pursue areas that interest your students and to customize the quickly-changing information regarding important societal issues such as climate change and cell phone technology. Textbooks are usually at least 4-5 years out of date by the time they are published, may not be at a reading level that all students can access, and often do not address students’ interests.
In my opinion, creating phenomena-based learning, generating student-led discussion, and offering labs/projects on which students can have input are much better vehicles for learning at the high school level than checking off chapters in a textbook. However, it can be challenging to guide your students toward your academic and skill-based objectives. Students sometimes ask questions that are not on topic, or are way beyond what they can currently understand.
I like to place all student questions in a “parking lot,” along with their initials. This is a large piece of paper or white board where questions can be listed and checked off as they’re addressed; or, for questions that are too advanced, the instructor can indicate which unit will eventually get to them. This recognition of student thought encourages even shy or reluctant students to ask questions, because the questions are not simply “dismissed,” but rather addressed with respect and recognition. Also, in a heterogeneous class, you will have lots of students that come in with a variety of skill levels.
The advantage of an “organic” inquiry course is that students will naturally want to do activities that match their abilities as well as their interests. I will often give students a choice of three different activities or labs that have different levels of difficulty (but the same length on paper) so that they can choose which one they would like to do.
I find most students choose activities that challenge but do not frustrate them. Being flexible does not mean throwing your academic objectives out the window, but rather letting students help you find more interesting paths to achieving them. Most importantly, enjoy the ride, and create lessons that are fun and exciting for both you and your students.