Since the summer of 1999, groups of modeling teachers have worked at Arizona State University to try to organize the topics students ordinarily study in high school chemistry around a series of particle models of increasing complexity. In 2005 we began an effort to develop a Modeling Workshop for chemistry with a design parallel to that used in the Modeling Workshop in mechanics. In June 2005 we conducted a pilot workshop in chemistry at ASU. By summer’s end in 2013, over 800 teachers have taken Modeling Chemistry workshops nationwide.
The curriculum design was influenced by the CHEM-Study approach which first appeared in the early 60′s. Our work makes the particle models used to describe matter and the treatment of the role of energy in change more explicit. The three questions that guide our approach to understanding chemistry are:
- How do we view matter? (Answer in terms of the particle you are using to describe matter)
- How does it behave? (Provide an explanation of the behavior using this particle model)
- What is the role of energy in the changes we observe?
In traditional chemistry curricula, students are introduced right away to the modern model of the atom and asked to accept all its complexities as a matter of faith. By contrast, our approach is to start with a simple model of the atom and show students that our model evolves as the need for a better one arises. In each of the instructional units we move from examining phenomena to the patterns we impose on the phenomena to the models we build to help us explain phenomena. Our treatment of the role of energy in both physical and chemical change is sufficiently different from the piecemeal approach found in most curricula that you will want to review it pretty thoroughly before you attempt to teach it. We have also included two evaluation instruments. The Matter Concept Inventory is an assessment of student understanding of the particle nature of matter. It was originally intended for use with an 8th-9th grade physical science course. The Assessment of Basic Chemistry Concepts (ABCC) is adapted from the Chemical Concepts Inventory developed by Doug Mulford (JChemEd-2002). We have modified it to make it more appropriate for use with high school students.
What follows is the story line we have used to uncover chemistry. The curriculum materials have undergone testing at our high schools for ten years and have been used in workshops since 2005. Major contributors include Joy Shrode, Brenda Royce, Larry Dukerich, Ray Howanski, Tammy Gwara and Dr. Guy Ashkenazi. If you have any questions, comments or concerns, you should direct them to Larry Dukerich or Brenda Royce.
Outline of curricular materials
- Simple Particle – Describing Matter: Matter is composed of featureless spheres (BB’s) which have mass and volume. These particles are essentially the “atoms” proposed by Democritus.
- Simple Particle – Energy and States, part 1: Our BB’s are in constant, random, thermal motion, the speed of which depends on the temperature. The BB’s interact with one another by collisions.
- Sticky Particle – Energy and States, part 2: Our BB’s also exert attractions on one another. Energy is a conserved substance-like quantity that is stored in various accounts and transferred in various ways.
- Bonded Particles – Describing Substances: The particles that make up substances can be compounded from smaller particles. The fact that compounds have definite composition leads us to Dalton’s model of the atom. Evidence from combining volumes and definite mass composition allows us to deduce formulas of compounds.
- Counting Bonded Particles – the Mole: From Avogadro’s Hypothesis we are able to count molecules by weighing macroscopic samples.
- Particles with Internal Structure: We find that atoms have the property of charge and some internal structure; we use the Thomson model of the atom to account for our observations.
Because many chemistry teachers report that they need to address the internal workings of the atom in the first semester (due to district tests), we suggest that they could do units 10 & 11 (in Chemistry-Beyond Core) right after Unit 6. They could then return to Units 7 – 9.
- Representing Chemical Change – Particles and Energy: Chemical reactions involve the rearrangement of atoms in molecules to form new molecules. This rearrangement of atoms results in a change in the chemical potential energy (Ech ) of the system. This invariably produces changes in thermal energy (Eth ), and results in energy transfers between system and surroundings.
- Stoichiometry 1: Equations representing chemical reactions relate numbers of particles (molecules or formula units) to weighable amounts of these particles.
- Stoichiometry 2: Equations representing chemical reactions can also relate numbers of particles (molecules or formula units) to volumes of gases, solutions and to the change in chemical potential energy.