Evolving

“Failure is simply the opportunity to begin again, this time more intelligently.” – Henry Ford

The above is a quote that used to hang on the wall of my classroom, when I taught in a place where I had a classroom to myself and decorating choices were entirely up to me. It was meant to be encouraging to my students as they progressed through a year of chemistry, through a year of struggle and growing and learning. Our education system is designed in such a way that students feel they must always find the right answer, and find it quickly, or they have failed to meet some imaginary mark that measures their worth. Rarely do we reinforce struggle and failure in the education system as the most effective way to grow, so I wanted to remind my students that perfection, especially rapid perfection, was not the goal of the course.

Upon reflection I have found that I could be living up to this quote more fully in my professional career. I would not describe the last few years of my teaching career as a failure. Far from it. However there is (as there always is) much room for improvement, and this year I am intent on seizing those opportunities, challenging myself as an educator, and learning through my own struggle and failure.

I spent several years teaching at a high school in Arizona. In that environment I effectively employed a methodology of instruction known as Modeling Instruction. (If you are not familiar, I highly recommend you check out the American Modeling Teachers Association site for more information.) In 2013, I moved across the country to teach at a school in New York City. The last two years have been a steep learning curve for me as I adjusted to a new city, a new school, new colleagues, and students who had different needs than those I had experience working with.

After two years at my school in NYC, I believe I have a firmer grasp on who my students are and what they need. As those who attempt National Board Certification know, we as teachers must always evaluate these kids, at this time, in this setting when making decisions about what will happen in the classroom. This year I will be making some changes in how I approach Modeling Instruction in the classroom, changes that I am making based upon the needs to my particular student population.

In this blog post, I will describe the year outline that I used in past years, and then the outline I will be using this year, as well as some of the reasons behind my changes. Future blog posts will provide more detail about specific changes, as well as reflections on how the year is progressing.

Old Sequence

U1 – Properties of Matter

Students begin to develop a basic particle model through completing experiments on mass, volume, and the relationship between mass and volume. They collect macroscopic evidence that mass is conserved, that 1 mL is equal to 1 cubic centimeter, that the ratio between mass and volume is a constant for a substance, and that constant is called density, and that the density of most gases is several orders of magnitude smaller than the density of most solids and liquids. Microscopic (particle level) explanations are given for each of these ideas and they are visually represented by drawing particle diagrams.

U2 – Energy and States of Matter I

Through macroscopic evidence, the students’ particle model evolves to include the idea of motion. All particles are in motion and particles in warmer substances are moving faster. The property of pressure, in particular gas pressure, is defined and discussed, and then students carry out experiments to determine the relationships between gas pressure and a gas’s temperature, volume, and amount of particles. Due to the proportionality of these relationships, problems can be solved involving the effect on one variable by the changing of any of the others. The gas laws are defined as predictors of gas behavior, and an explanation for why gases behave this way is given by the kinetic molecular theory. Visual representations of both laws (graphs and equations) and theories (particle diagrams) are discussed.

U3 – Energy and States of Matter II

Beginning with a paradigm lab to find a relationship between temperature and energy, students are asked to take a sample of ice and supply constant energy until the sample of water has reached its boiling point and been boiling for several minutes. Temperature readings are collected every thirty seconds and a graph of temperature vs time is made. As students see from the graph, there are times when energy is added to the system, but no change in temperature occurs. From this macroscopic evidence and energy model is developed that explains sometimes energy causes changes to particle motion and sometimes it causes change to particle arrangement. This model is visually represented with energy bar charts and particle diagrams. The proportional relationships between energy and a substance’s mass, change in temperature, specific heat capacity, heat of fusion, and heat of vaporization are determined in order to quantify the energy model.

U4 – Describing Substances

Through macroscopic observation of properties, the difference between elements, compounds, and mixtures is discussed and particle model representations are agreed upon. Evidence for the tenets of Dalton’s model of the atom are gathered through thought experiments, virtual experiments, and in class experiments. Avogadro’s Hypothesis is discussed and used as evidence to support the particle model. The laws of Definite and Multiple Proportions are discussed and used as further evidence to support the particle model. Percent composition by mass data is used to begin to hint at the idea of determining empirical formulas for compounds.

U5 – Counting Particles

The concept of relative mass is introduced and applied to elements. Some evidence for how the relative masses of elements were determined is presented. The mole concept is introduced in order to begin counting particles of elements and compounds in groups. Calculations involving molar mass are introduced. Students experimentally determine the empirical formula of a compound in order to see how mass data can be used to infer a particle ratio.

U6 – Particles with Internal Structure

This unit begins by collecting experimental evidence that can be used to support Thomson’s model of the atom, an atom with mobile, negatively charged electrons. Conductivity, defined as freedom of movement of charged particles, is used as an observable property that can help us distinguish between metallic and nonmetallic elements. Observations of aluminum foil and paper strips interacting with a charged piece of tape can be explained using Thomson’s model and differences in the ability of the electrons to move in the substance. Conductivity as a property is further used to distinguish between types of compounds, molecular and ionic. X-ray crystallography evidence of particle structure (using Mercury software) is used to distinguish between different types of fundamental repeating particles: atoms, molecules, and ions. Ionic compounds are discussed in depth, and the electrolysis of copper (II) chloride can be used as evidence for metals as cations and nonmetals as anions. Patterns of empirical formulas are used to determine the most likely charges of the representative elements. Comparing the conductivity of binary ionic compounds and polyatomic ionic compounds can be used as evidence for the number of ions a compound dissociates in to.

U7 – Describing Chemical Change

Through experimentation, students describe chemical reactions as a rearrangement of particles. Particle representations of chemical reactions demonstrate and reinforce the Law of Conservation of Mass. Patterns of chemical change are recognized and students write, balance, and predict products of chemical reactions. The energy model developed in unit three is revisited and the relationship between thermal energy and chemical energy is flushed out. Double and single replacement reactions are examined more closely as experiments about solubility rules and the activity series are carried out.

U8 – Stoichiometry Basics

Utilizing a Before-Change-After (BCA) table, students are able to keep track of changing mole quantities in a chemical reaction. BCA tables, like ICE tables used in equilibrium problems, keep track of increasing or decreasing amounts of the substances based on the mole ratio of the balanced chemical reaction. In this foundational unit, only stoichiometry involving mole and mass calculations are addressed.

U9 – Applied Stoichiometry

After 8 units, students have a solid foundation of information in chemistry. This unit revisits several topics and provides more depth and breadth to what is already known, all under the umbrella topic of quantitative analysis of chemical reactions. Gases are revisited as Dalton’s Law, molar volume, and the Ideal Gas Law are introduced. Mixtures and solutions are revisited and molarity is introduced. And finally, energy is revisited by introducing the concept of heat of reaction. These seemingly unrelated ideas are all connected together as information that is necessary to do chemistry calculations involving the mole.

U10 – Chemical Equilibrium

As students have grown accustomed to analyzing chemical reactions, both qualitatively and quantitatively, we can now begin to discuss how that works if a chemical reaction proceeds in both directions. To begin the unit, we develop a sense of collision theory and conceptual ideas of kinetics. Students learn to describe particle behavior in chemical reactions according to probability. The Law of Mass Action and Le Châtelier’s Principle are both addressed.

U11 – Acids and Bases

Students first develop an idea of what acids and bases are, based on their behavior with acid-base indicators. Then, using universal indicator, “levels” of acidity are noted and defined based on concentration of hydrogen ions. The pH scale and its meaning are discussed. Finally, neutralization reactions are modeled based on students’ prior understanding of reactions and molarity. Titration curves are examined. If time permits, strong vs weak acids may be addressed.

U12 – Models of the Atom

A hydrogen gas lamp viewed through a spectroscope at the beginning of this unit provides a situation where the current particle model (Thomson’s model) is no longer sufficient. Through research projects about the major contributors to the model of the atom, students develop a more complex model, understanding the history up through Bohr’s model. Connections between the atomic model and the Periodic Table, with regards to atomic number and atomic mass, are discussed.

U13 – Periodic Table and Bonding

Ionization energy and atomic radius data are used to develop a more detailed version of Bohr’s model. This model can be used to explain the trends we see in ionization energy and atomic radius, as well as the charges formed by most elements when they form ions. Ionic bonding is described as an electrostatic attraction between two charged ions. Models of “combining power” of elements, based on empirical formulas of hydrides, are used to develop a model to begin to describe molecular compounds. Through evidence, the description evolves until Lewis structures are introduced as a model of covalent bonding. An understanding of electronegativity is developed through examining thermochemical data, and electronegativity is used to help determine which structures of compounds are most energetically favorable.

New Sequence

U1 – Science Skills: Measurement and Calculations

My particular population of students come into chemistry already having a firm grasp on the concepts of mass, volume, and density, as well as differences in states of matter. The design of this unit will still contain this content, but will put a much heavier focus on skills needed in a science classroom. Post lab discussions will emphasize more about sources of uncertainty, how to take good measurements, and how to connect content knowledge with experimental evidence.

U2 – Energy and States of Matter

A particle model of matter that includes motion as related to energy will still be developed at the beginning of this unit, as described in unit 2 above. However, instead of then going into gas pressure, we will instead focus on the energy model development directly from here. Much of this unit will be what is referred to as unit 3 above.

U3 – Models of Particle Motion

Now that students have a model of how motion of particles can change with the addition of energy, we will more fully explore this idea. Thermal expansion of solids and liquids will be discussed and described at the particle level. The difference in the ability of gases to expand in comparison to solids and liquids will be pointed out as a lead in to a lab about the relationship between temperature and volume of gases. This lab will also be used to launch into a discussion about gas pressure, as students will be coaxed to recognize that pressure is held constant in the temperature vs volume lab. This will lead in to much of the material described in unit 2 above. In addition a more explicit discussion of Kinetic Molecular Theory will happen as we work to build a model of molecular motion.

U4 – Describing Substances

This unit will be much the same as unit 4 described above, though there won’t be as much emphasis as empirical evidence used to begin determining compound ratios.

U5 – Models of the Atom

This unit will be very similar to unit 12 as described above. The transition to this unit, however, will now rely on the development of Dalton’s atomic model in the previous unit.

U6 – Describing Compounds

This unit will be much the same as unit 6 described above, though the students will already have a more complex model of the atom to start with than Thomson’s model. This unit will now be taught with even further emphasis on the idea of how macroscopic evidence leads us to believe things about chemical substances. The next unit will then provide a theoretical, submicroscopic explanation for why everything students observe in this unit are true.

U7 – Periodic Table and Bonding

This unit will be much the same as unit 13 described above. However strong connections will be made to the macroscopic evidence collected in unit 6.

U8 – Counting Particles

This unit will be much the same as Unit 5 described above.

U9 – Describing Chemical Change

This unit will be much the same as unit 7 described above.

U10 – Stoichiometry Basics

This unit will be much the same as unit 8 described above.

U11 – Applied Stoichiometry

This unit will be much the same as unit 9 described above.

U12 – Equilibrium

The design of this unit will be determined at a later date.

U13 – Acids and Bases

The design of this unit will be determined at a later date.

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2 thoughts on “Evolving

  1. I’m using the physical science modeling materials with my freshman & the bio teacher at my school is very interested in attending the modeling institute for bio. If this happens, the adjusted chem plan you proposed would work out really well for students who have been taught exclusively by modeling when I see them again as juniors. Good luck this year!

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