Given the diverse background of my students, I will use a variety of strategies to engage and deepen understanding across learning modalities. Students will use models to gather data using inquiry skills. These models will take the form of labs to model and Physics Education Technology (PhET) Interactive Simulations, or other online demonstrations. PhET interactive simulations are java based online demonstrations (Weiman, n.d.). These online labs are an excellent way for students to work through online simulations of labs, with the benefit of seeing the usually “unseen.” For example, students can often visually track atoms, molecules, electrons, and even energy in lab settings.
The inquiry process is very important for student learning, as it allows for student self-discovery of fundamental chemistry concepts. Self-discovery reinforces student understanding by challenging conceptions, and having students critically think through data to reach their own conclusions. Once students have explored a chemical concept, they will model the content they have learned via visual, physical, and quantitative models. They will then work with their peers to expand upon their initial understanding with each additional lesson and lab. Finally, in order to solve the community issue, students will apply their final model in a culminating project.
Demonstrations, Labs, and Activities.
1. Conservation of Energy and Heat Transfer activities
In the PhET online simulation, “Energy Transformations and Change” students have access to two labs (Weiman, n.d.). The first lab, “energy systems” is on the second tab, and involves students building a three-part machine with an input, a turbine or solar panel, and an output. As the machine runs, students can watch energy flow through the machine. The online demo specifically labels the different types of energy running through the machine, students can determine if each type is potential or kinetic energy. Students should be able to conclude that the energy from the input is the same amount of energy in the output, and therefore energy cannot be created or destroyed. Students can build up to describing the energy flow in any household product, such as a blender (electrical energy to kinetic energy) or a flashlight (chemical energy to electrical to light energy).
In the second lab “Introduction,” on the first tab, students look at the heat flow of energy from fire into three objects: a bucket of water, a brick or an iron block of equal dimensions. Students can heat up the two blocks with a fire, or cool them down with the ice. Then students can stack the two blocks and watch the flow of energy from the hot object, to the cold object. Students will see that the energy stops flowing when the two bricks are at the same temperature, not necessarily when they have the same amount of energy. Students can then visualize that the brick does not need as much heat energy to be at the same temperature as the iron—creating a basic definition of heat capacity.
Students can perform a hands on version of this lab to practice quantitative calculations. Students will first boil 100 g of water, then place a solid in the beaker with a thermometer. The solid should have a known mass. while waiting for the temperature of the contents of the beaker to rise, measure the initial temperature of a beaker of cold water. Once the temperature of the water and solid reaches 70
C, carefully remove the solid from the hot beaker and into the cold water beaker. Students should then measure the change in temperature of the water. Students can now work in pairs to calculate the heat absorbed by the water, and the specific heat of the solid, as well as the heat used in the phase change.
2. Entropy “Boltzmann Game”
Entropy is a particularly hard example for students to grasp. For this, give students a plastic bag with 20 puzzle pieces. Each round, have students shake the bag and then lay out the pieces on their desk. Then students will count how many are face up, and how many are face down. Students will repeat this processes up to 10 times, counting how many are face up and how many are face down. Either a student volunteer or the teacher will keep record of how many groups only had 1 flipped, 2 flipped, etc. each round. Afterwards, students will make a conclusion on what the most likely positions of the puzzle pieces were, citing evidence from the class data. Students should be able to show that having all the pieces all in one formation is extremely unlikely, while having the pieces 50/50 flipped is more common. This lab can be used as a jumping point to start a conversation on entropy as it relates to phase change and reactions.
3. Phase Changes Play and Lab
To review the vocabulary of phase change, students can participate in an acting game. Students begin this activity with a warm up, drawing what the particles look like in each of the main phases (solid, liquid, gas). Students are then split into two groups, and one group takes notes, while the other acts out the different phases. While the half is acting out the different phases, the note-takers must figure out what phase is being acted, and a relative amount of enthalpy and entropy. Students can then change spots, and reflect at the end, reviewing the different components of enthalpy and entropy in phase change by matching their answers to the acted scenes.
4. Chemical Changes Labs and Word Search
Students can differentiate between physical and chemical changes by looking at some hands on demos. One demo could be ripping steel wool into small pieces, versus burning steel wool. Another, melting 1 mg of sugar, versus burning it. Students work in small groups to draw what they see in each condition on a whiteboard, then discuss the differences are on a molecular level between the two conditions. After a set amount of time groups will perform a gallery walk in which students leave out their work for their peers to look at and provide comments on sticky notes, as the students rotate around the room. Students will then discuss the differences between the two in a large group, and how physical versus chemical changes are measured. Finally, students will edit their model and write final conclusions including ways to differentiate between the two.
Another activity is a card sort. Students must sort through cards of images that show either a physical change or a chemical change, separating them into different categories. Examples of cards include: baking a cake (chemical), breaking a window (physical), cutting bread (physical), burning a log (chemical). Students must share their reasoning for how they sorted, looking for patterns in what differentiates a physical versus a chemical change.
5. Rates of Reaction Labs
Students can explore what affects the rate of reaction by measuring the time to completion of a common reaction, such as alka-seltzer dissolving in acetic acid, and then changing the properties to see how they affect the completion time of reaction. For example, students can see what happens when they increase the surface area by crumbling the pack of alka-seltzer, or increasing the temperature of the acetic acid, or diluting the acetic acid.
Another minilab to test the effect of surface area includes aluminum foil in 1M hydrochloric acid, smoothed or crumpled (goggles should be worn for this, and other safety precautions observed). A way to test temperature is by cracking a glow-stick and watching which one lights up faster in a cold, hot, or room-temperature water bath. To show the power of a catalyst, students first mix soap and hydrogen peroxide in a bottle, seeing no immediate reaction. Then students add the catalyst, yeast, and the mixture quickly changes form, expanding as a foam out of the bottle. Looking closely, the yeast can still be seen after the reaction as they have not been ‘used’ up.
To practice differentiating between endothermic and exothermic, students will measure the change in temperature of two different solutions: baking soda and vinegar, versus baking soda in water and calcium chloride. The baking soda and vinegar solution should decrease slightly as it is endothermic, while the baking soda solution and calcium chloride solution would heat up as it is exothermic. After each lab, students should calculate the change in enthalpy and then draw a graph of the reaction progression correlating numbers from their lab; although students will have to predict the activation energy necessary to reach the transition state.
Project Based Learning Strategy
This unit could be tied into Project Based Learning (PBL), in which students can solve a community based problem in a culminating performance task (What is PBL?, 2014). These culminating tasks typically combine student understanding of scientific content with 21
century skills in communication, collaboration, creativity, and critical thinking. This structure specifically engages students in content, lends a hand to differentiating by skill and interest, and allows for increased opportunity to work with literacy and problem solving. Furthermore, students will be engaged by a community problem, asking them to develop their critical consciousness of society, and to expand their leadership to help their community.
PBL Unit Outline
Anchoring Phenomenon -> Model Development -> Application to Community Issue
Students will be introduced to the anchoring phenomenon in an entry event. It must be relevant to the student, engaging, and spark student curiosity. In this lesson students are introduced to the phenomenon in a video or reading. I would recommend the anchoring phenomenon of a spontaneous chemical change, such as the Breaking Bad clip of Season 1, Episode 6 (Hughes, 2008). One could also introduce the community issue of exploding Takata airbags (see below) as the anchoring phenomenon (Tabushi, 2014). If including physical changes in this unit, a second phenomenon could be of a physical change such as a clip of an exploding water heater (Dallow & Lentle, 2007). Students would then explain what they think is happening in the two clips, comparing and contrasting the two. This initial model could be a written, verbal, or visual explanation, although a combination of all three will be required throughout the unit. Students will then generate a list of questions they would like to answer to be able to explain their model in more detail.
Each lesson throughout the unit has the goal of answering an essential question. At the end of each lesson, students should go back and revise their models to include the new information. This strengthens students’ skills in the engineering process and modeling skills. Models are created in small groups of 2-4 students to allow for collaboration. Students must explain their understanding to each other, and support their understanding with evidence from content, research, or experiments—strongly tying into English/Language Arts (ELA) standards for supporting arguments with evidence (RST.11-12.1).
Essential questions should cover the content but also be specific to the student generated question list. Questions that appear on the student created list, but are not already covered in the content, can either be added in, or student taught. That is, the additional questions are assigned to students and the students research the answers from a variety of sources (i.e., internet, textbook, teacher, etc) and report their findings to the class. This technique is similar to flipped classroom, allowing students to take charge of their learnings, with the added benefit of strengthening science communication skills.
Application to Community Issue
In the concluding stage of PBL, students finalize their understanding of the model, and begin to apply and create a new technology to solve a community issue. The community issue is typically introduced in the entry event, or part way through the model development. A suggested project is designing an automobile airbag.
Airbags utilize a chemical reaction that releases a gas to expand the airbag, allowing for enough pressure to cushion passengers during impact in a crash. In a classic airbag, the mechanical energy of the crash is utilized to compress a spring, this energy is then transformed into electrical energy that ignites a detonator and sets off a decomposition reaction of sodium azide into nitrogen gas that expands the airbag (Shipman, 2009). It should be noted that sodium azide is both extremely explosive and toxic, as are other propellants typically used in airbags. In fact, airbag company Takata recently came under scrutiny for using a cheaper, yet even more explosive propellant, ammonium nitrate, in their products (Tabushi, 2014)and a Texas teen died in early 2016 from an airbag explosion (Press, 2016).
In partners or small groups, students will be asked “How can we design an effective and safe airbag?” Students would first start with modeling the energy changes throughout the process, starting with the mechanical energy of the impact. Students would then pick between two options to inflate their bags: dry ice, a physical change, or sodium bicarbonate and vinegar, a chemical change—and explain the difference between the two. Students then conduct labs to measure temperature changes, and to model a calculation of Gibbs free energy. Students would be required to market their airbag in a creative way as long as they incorporate all the scientific concepts supported with graphs showing the physical or chemical changes. Marketing should include specifics on what would speed up the chemical reaction, or the kinetic changes (quantified) in the physical change. This project covers the four 21
century competencies of creativity, communication, critical thinking, and collaboration.