Chemical Education Article
Project STEP (Science and Technology Enhancement Program) is one community partnership taking aim at improving STEM (Science, Technology, Engineering, and Mathematics) skills and communication. Funded by an NSF (the U.S.A. National Science Foundation) GK-12 grant in 2001, Project STEP is based at the University of Cincinnati in Ohio, U.S.A. Although operated and managed at the university level, Project STEP is a true community partnership currently interacting with six local secondary schools involving 24 secondary science, mathematics, and technology teachers. Directly in contact with these teachers and students for 10 hours each week are six university graduate students, called Fellows. The graduate Fellows also work in conjunction with their research advisors while involved with Project STEP.
The graduate Fellows are the focus of both the grant and this article. Accordingly, goal one of Project STEP emphasizes a need for improved communication of STEM subjects by the graduate Fellows, or in other words the future faculty of STEM disciplines. With these graduate Fellows interacting with secondary students and teachers on a weekly basis, their ability to explain the research that they do becomes more succinct, efficient, and knowledge level appropriate.
The graduate Fellows are required to create five major lessons during the academic year for use in the secondary classroom. These lessons must contain measurable objectives, a STEM focus, an engineering connection, a hands-on activity, both pre/post assessments, and an ending review. Graduate Fellows are free to create lessons that reflect both their personality and their expertise in STEM content. Three of these chemistry lessons are highlighted in this article, and each of these lessons has been or will be taught in local Cincinnati area secondary schools.
Lesson by Carol Clinton, Engineering PhD Fellow:
In this lesson, students use physical manipulatives (cardboard models with repositionable adhesive paper strips to simulate outer shell electrons) to gain an understanding of how atoms combine to form molecules based on the configurations of electrons in the outer shells, how molecules break and atoms recombine into new substances during chemical reaction, and what it means to balance the equation representing the reaction. 
There are three reactions discussed. Exothermic (liberates energy) and endothermic (requires energy) reactions can have practical uses, such as hand-warmers, and medicinal cool packs. Understanding whether to expect temperature changes during reactions is important for chemical engineers in designing processes (can cause explosions, runaway reactions, etc). Ionization, another type of reaction, allows “road salt” to function in lowering the freezing point of water and keep highways safer.
Some objectives include that students will correctly identify the atoms and their ratios that comprise desired molecules, construct the target molecules, rearrange the atoms to create the desired end product chemical molecules, and create the balanced chemical equations that represent the reactions.
To catch the students’ attention use the demonstration “Hot and cold packs.”
Reaction 1: Put 1 tsp. CaCl2 in a clear plastic zip bag with 10 ml of water. Pass around class to observe (dissolves and liberates heat).
Reaction 2: Put 1 tsp NaHCO3 in a clear plastic zip bag with 10 ml water. Pass around class to observe (dissolves and gets cold).
Reaction 3: Pour one solution into the other bag and reseal. Pass around class (carefully) to observe (bubbles of CO2 form and fill the bag – be careful not to let it pop). Extension: Add phenol red indicator and expand discussion and lesson to cover pH. The CO2 will form in a weakly acidic solution.
Classroom content will include the demonstration of cardboard models to construct a water molecule and describe dissociation into Hydronium (H+) and Hydroxide ions (OH-), with the hydronium ion leaving its electron – resulting in a positive charge, and the hydroxide ion having the extra electron and therefore a negative charge. Show how H2 and O2 must react in a 2:1 ratio to create 2 H2O molecules, and write the balanced equation on the board.
Explain that these cardboard “atoms” are gross oversimplifications of actual atoms…MUCH larger than actual. Actual atoms are 3D. Electrons are always in motion in clouds (not circular tracks). Bond positions are not in co-planar 900 orientation. Electrons are the same, no matter where they begin.
The students use cardboard models to combine “atoms” to form the starting molecules for reaction 1 (CaCl2 and H2O). Fit the cardboard shapes together and “bond” with the re-positional adhesive strips). Take apart to show dissociation, leaving the electrons from Ca on the Cl atom creating Ca+2 and 2 Cl.- Repeat for reactions 2 and 3. Reaction 3 will require balancing.
In use with two secondary classes, totaling 46 students, average improvement in balancing equations was 150%. Additionally, student feedback indicated that they liked the activity, learned a lot from the lesson, were more interested in learning about engineering, and felt more confident in their abilities to learn science and math. The exact chemistry of the reactions includes:
- CaCl2 + H2O -> Ca+2 + 2 Cl- + H2O (which is actually H+ + OH-; or more correctly 2H2O is H3O+ + OH-). The heat is from breaking the bonds in CaCl2.
- NaHCO3 + H2O -> Na+ + HCO3- . Breaking this bond requires energy.
- CaCl2 + NaHCO3 -> CaCO3 + 2 NaCl + H+
H+ + NaHCO3 -> CO2 + H2O + Na+. It is the CO2 gas that forms bubbles and fills the bag. If you are also using the pH indicator, this step forms a slightly acidic solution which will change the indicator color.
This lesson requires preparation time to create the atom and electron models. This is a good robust basic lesson, with interesting possible extensions into pH, polymers, or other topics.
Lesson by Fee Mtshiya, Engineering Masters Fellow:
This lesson is titled Molecular Shapes: Using Valence Shell Electron Pair Repulsion (VSEPR) Theory and Lewis Structures. The primary objective in this lesson is to learn how to use the VSEPR theory to predict the shape of molecules, based on knowledge of Lewis Structures. What should really stand out to the students in the lesson is how a 2-Dimensional view of molecules moves to a 3-Dimensional view using the VSEPR theory as a tool.
One of the ideas that Project STEP emphasizes in its lessons is ‘Application to Real Life’ such that the students can make a clear connection between the subject matter and materials, objects, and events in their everyday lives. In this regard, the catch for this lesson is looking at the hormone ethene using tomatoes and pipe cleaners. Two tomatoes, one ripe and one green, are brought in and the teacher shows them to the students. The question being asked is, ‘What is the difference between the two?’ The difference is that the ripe tomato has more of the hormone ethylene (C2H4) which tomatoes release as they ripen. The teacher then puts together sections of pipe cleaners rolled into circles to represent the ethene molecule. Three colors of pipe cleaners are used. One color represents carbon, another hydrogen, and the third the electrons that connect the two elements (these are smaller circles).
After a short but thorough explanation of what the VSEPR theory is and how it is used to predict molecular shapes based of the Lewis Structure, the teacher presents the primary molecular structures to the class. The students are divided into groups. One draws the Lewis Structure of a particular molecule on the board and the other uses circular pipe cleaners of different colors to represent the molecule 3-dimensionally (similar to what the teacher did in the catch). The teacher explains the electron spacing in the molecule, how they interact, the name of the molecular shape, the bond angles, and any other important points to remember about that particular shape. After this, a power point slide of the correct molecular shape is shown and other slides are shown with additional examples of molecules with that molecular shape.
Lesson by Gabriel Wickizer, Engineering Masters Fellow:
In this lesson energy flow is shown in household appliances. The first day begins with coffee. A vacuum coffee pot makes it easy to discuss the concept of the energy system and to promote inquiry into energy flows. The coffee pot demonstrates the conversion of heat energy into work as water is raised from a lower chamber to an upper chamber where the coffee grounds are held, only to be sucked back into the lower chamber once removed from the heat. Students are then presented with a typical kitchen from rural Guatemala. The kitchen is presented and then shown to represent an energy system schematically. With definitions in hand, the students label a handout of the same diagram with vocabulary such as “system”, “heat”, “pv-work”, and more. An open discussion of some essential concepts and questions ensue once the worksheets are completed. At the end of the first day, the students are assigned the task of reconstructing the exercise using a meal that each might cook in his/her own home.
The second day begins in the lab. Students compete in a taco-making contest, the goal of which is to pack as much food energy as possible into a specific volume. Practical uses of this energy in the human body are discussed. The instructor emphasizes that, no matter the use of food energy, some flows as heat energy, while some is used to do work. Thus, enthalpy is shown as a convenient indicator of the total energy of a system in a chemical reaction context.
Students observed a brief derivation of enthalpy in parallel with a representation of the chemical reaction which provided the flame for making coffee on the previous day. The enthalpy change of a system was thus related to more formal representations of chemical equations in preparation for the concepts of Hess’s Law and entropy.
In retrospect, this lesson will be dangerous to implement if ample time is not given for setup. It is the author’s suggestion to switch the sequence of kitchen examples from “Guatemala, then at home” for “Home, then in Guatemala.” Overall, the assessment tool indicated that 30% of students improved in all assessed content areas.
Conclusion:
These lessons showcase just four of over a hundred lessons that have been created by graduate Fellows since 2001. There are two websites that highlight engineering applications of math and science like these. The first is the Project STEP website (www.eng.uc.edu/STEP) where all of the lessons created can be viewed without charge. The second is also a free collection of STEM activities, lessons, and units involving engineering called Teach Engineering (www.teachengineering.com).
The conclusions from Project STEP are broad, but carry far reaching implications. First, community partnerships between university and sec
ondary schools are not only possible but necessary for continued STEM development. Second, graduate Fellows, secondary teachers, secondary students, and university personnel benefit from these types of community partnerships. Third, the promotion of STEM disciplines is of utmost importance for a sold base of citizens prepared to tackle new challenges as time goes on. Project Step is committed to the community partnerships established and all three goals (Fellows, students, and sustainability) for the promise of increasing communication, content knowledge, and interest in STEM careers.
