Mass Spectrometry: Using a Game Format to Develop Logic Skills While Applying Fundamental Chemistry Knowledge to Determine Possible Chemical Formula Represented in Graphic Output From A Mass Spetrometer

This mini-unit is designed to train students to use logic to analyze data and formulate accurate scientific interpretations. The students will be required to synthesize a number of chemistry concepts in order to complete the steps for accurate interpretation of mass spectrometry data. The students will also gain an appreciation for the application of chemistry knowledge and logic skills in the real world. Key terms in this unit include organic chemistry, formula mass, isotope, structural formula, mass spectrometer, molecular ion, relative abundance, and weighted average.

There are a number of concepts that are keys to students' success in this unit. Student will be focusing on organic molecules and therefore become more familiar with the elements commonly found in organic chemistry. Furthermore, they will be exposed to the technology of mass spectrometry and its uses as well as its limitations. Additionally, students will review the concept of isotopes and take a closer look at how the atomic masses in the periodic table are calculated using a weighted average of existing isotopes for a given element. Finally, students will review the valence state of atoms common in organic chemistry and apply bonding rules to draw structural formulas.

This unit could be used as a tool for teaching some or all of the concepts included, or better yet, it can be presented as a review unit where students can apply previously learned concepts such as formula mass, isotopes, covalent bonding, and ionization in the process of reading mass spectrometry data. This lesson may be best suited to students in high school chemistry or advanced chemistry courses. Because the learning process is peer-assisted, these activities work with the full range of class sizes as long as there are some some quick learners to help struggling students. It is designed to be a unit that challenges the problem solving abilities for students at this level and therefore one must expect students to struggle with problems during the latter stages of the unit. All the activities included are done in the classroom without any additional equipment. Atomic and molecular models are an option that can be used and would therefore be needed if so desired. The amount of time needed would range from one to two weeks depending on the average performance level in your classroom. The difficulty of the unit assessments and pace can be adjusted to some degree to meet the performance level of the class, but the ultimate outcome, students being able to interpret output from a mass spectrometer, is what it is.

This lesson on mass spectrometry is set up as a series card games that deliver the necessary skills in incremental steps towards the ultimate goal of interpreting a mass spectrometer graph. I introduced the lesson as one that is usually taught at the college level, but assure students they are a very smart group of students and I believe they can handle it. Giving students the idea that mass spectrometry is a major area where scientists apply chemistry skills and giving some examples of how chemical identification plays a critical to our daily lives is a good way to open the unit. In addition, a basic introduction to how a mass spectrometer works along with some graphics from the internet make the processes occurring in the mass spectrometer more concrete and is a great review of mass, ionization, magnetism, & momentum.

All of the problems are presented to students on game cards with only one problem per card. Students work in groups of two and are given one card per student to solve together. Student really like the idea of being given their own, unique problem to solve and to raise the level of enthusiasm, the exercises are referred to as games; students often take to the challenge when presented as a game and a number of them thrive on competition. When we begin the exercises, I provide each student with an isotope sheet (see Isotope Sheet attachment) as a reference for the mass, relative isotope abundance, and the number of bonds formed by each element we will be working with. When a group has solved the problems presented on their cards, they check with the teacher who has an answer key and can give immediate feedback and additional cards as needed.

There are five different card games the students will "play", each one being a critical step towards reading the mass spectrograph (see Card Game Instructions & Sample Cards attachment). In the first card game, students calculate formula mass; a review of isotopes and how the mass in the periodic table is a weighted average should be done at the outset of this game. Next, students use the isotope sheet (see attachment) to calculate two possible masses for a molecule that contains an isotope and then graph mass (x-axis) vs. relative abundance (y-axis); they are creating their own mass spectrometer graph. In the third game students practice drawing structural formulas; this step can be accompanied by molecular model building and is needed so students can later confirm that molecular formulas they propose can exist following bonding rules. The fourth card game asks student to determine possible formulas for an organic molecule when given a formula mass and some additional information about what elements in contains. Finally, in the last card game, students tie it all together by interpreting a mass spectrometer graph and proposing molecules that could be represented by the graph. Open the Mass Spectrometer attachment for a brief overview of how a mass spec works along with a sample mass spectrometer graph interpretation, the final and highest order problem the students will attempt to solve. Isotope Sheet - student handout (Microsoft Word 32kB Aug25 09) Card Game Instructions and Sample Cards - for use by instructor and/or students (Microsoft Word 39kB Aug25 09) Brief Overview of How a Mass Spectrometer Works and Example Output Analysis (Microsoft Word 26kB Aug25 09)

Each game in the series is more challenging that the last; students will require more time for each successive step. Drawing structural formulas poses a problem for a good number of students so building models may be helpful, the caveat is that model building is very confusing for some students so extra time will be needed to get the most out of using models. Although I would always give students the chance to work through the problems with a minimal amount of assistance from the teacher at first, the final two card games ultimately require repeated modeling of the problem solving process by the teacher. Using skills of logic and problem solving to put all theses chemistry concepts together and interpret a mass spectrometer graph is a higher order thinking process that requires much patience and support from the teacher. When a student can solve such problems or even come close, it is important to recognize the significance of their achievement with enthusiastic delight. I did this lesson with students who had little background with the concepts covered; I am recommending it be done later in the year to give students the chance to review and integrate concepts learned in prior units. The emphasis of these lessons can then be placed more squarely on the use of logic to apply chemistry knowledge in the context of chemical identification with mass spectroscopy.

Informal Formative:
Individual-Pre-test
Group Work-Minimum of 4 correct solutions from each pair for each of the 5 card games.

Formal Formative:
Individual-Daily Quiz Question
Individual-Mid-unit quiz after the first three card games

Summative:
Individual-Post-test

9.2.1.1.4 Isotopes
9.2.1.2.1 Valence and Chemical Bonds