Identifying Chemical Reactions

1. Period 1: Presentation slides 1-8 (three-bags phenomenon, targets, reactants and products, physical change versus reaction, first quick check). W1 phenomenon worksheet (a second notice-and-wonder case: an iron nail in blue copper sulfate solution) after the bags, and W2 vocabulary relationships to close.
2. Period 2: Slides 9-12 (physical and chemical properties, the 'looks like a reaction' compare diagram, clue-or-proof check). Lab 1, the mystery powders, one session: students build a reaction fingerprint table for three known powders and use it to identify unknowns.
3. Period 3: Slides 13-17 (conditions that start a reaction, the stopping discussion, indicators, the clue-to-claim flow). Lab 2 session 1: six stations, record indicators, save products in labeled cups. W3 reading passage as homework.
4. Period 4: Lab 2 session 2: property tests on the saved products (solubility, recovery by evaporation, magnet, the leftover test), then the decision table and evidence-strength ratings. W4 diagram worksheet and W5 data worksheet follow the same logic and can be split between class and home.
5. Period 5: Slides 18-21 (the six properties that count, the aspirin task with its table, strongest-evidence check, the hot-bag discussion). Lab 3, the fizz-stops systems lab, one session; W6 CER on before-and-after data as the written assessment.
6. Period 6: Slides 22-25 (California rust connection, medicines by reaction, the aspirin timeline, the criteria check). W8 collaborative evidence sort in groups, then W9 transfer task on evaluating competing designs.
7. Period 7: Slides 26-28 (bubbles misconception, synthesis, exit ticket). W7 misconception repair, then W10 mastery as the quiz.

Materials overview: Every lab uses household chemicals only: baking soda, white vinegar, calcium chloride ice-melt pellets (check the label says calcium chloride with no other salts), Epsom salt, fine (0000) steel wool, 3% hydrogen peroxide, and active dry yeast, plus water. Also needed: splash goggles for every student, clear cups, zip bags, plastic spoons, droppers, a digital balance reading to 0.1 g (Lab 3) or 0.01 g if available, thermometers, a small magnet, a hand lens, and paper towels. No flames, no lead compounds and no nitrogen dioxide anywhere; the textbook's lead iodide, match and smog-gas examples are described on slides only. Calcium chloride solutions get hot; keep amounts small as written.

• Multilingual learners: Pre-teach reactant, product, physical change, precipitate and indicator with a picture card for each; post an anchor chart with 'clue' on one side and 'proof' on the other that stations are added to as the week goes; let Lab 2 observations be recorded with drawings and a home-language label before the English sentence; pair students so one reads the station card aloud.
• Students who need more support: Give the Lab 2 decision table with the first station worked as an example, a word bank for the fingerprint table in Lab 1, and a sentence frame for the CER ('Before, the ___ was ___; after, it was ___, so a new substance ___ because ___'). Reduce Lab 3 to four amounts of baking soda and provide the graph axes already scaled.
• Students ready for extension: Ask them to explain why the calcium chloride and baking soda station both fizzes and turns cloudy (two products form), to design a test that would tell the gas from Bag A apart from the gas from the yeast station without a flame, or to work out from Lab 3 how much baking soda a different volume of vinegar should use up.
• Students who need movement or alternative output: Run Lab 2 as true walking stations with a timer; allow the Lab 2 decision to be presented as a sorted set of cards on a clue/proof floor line; accept a recorded spoken explanation for the Lab 3 model and for the exit ticket.
• Students with limited vision or fine-motor control: Pre-measure powders into labeled cups so no student handles a balance alone; use large-print station cards and thermometers with digital readouts; let a partner pour while the student calls the observation and records on a device; magnet and temperature tests give non-visual evidence at most stations.

• One clue is not proof (pp. 154, 158). The book presents color change and gas formation as evidence of a reaction. Teach that bubbles, temperature changes, color changes and a solid appearing are indicators that something happened; boiling, a soda's fizz, dissolving calcium chloride (hot) and melting ice (cold) show the same clues with no new substance. Confirmation comes from comparing properties of the products with those of the reactants.
• Dissolving is treated as a physical change in this course, and the recovery test (evaporate the water, get the original substance back) is the student-level justification. Chemists note that dissolving an ionic solid in water involves real interactions between ions and water, which is why calcium chloride solutions get hot; keep this as teacher background.
• Recovery tests and temperature: a few dried drops of a solution are far too little to change the temperature of water measurably, and calcium chloride dried at room temperature comes back combined with water (a hydrate), which does not warm water as it dissolves the way dry pellets do; only a solid dried hot in an oven (teacher only) behaves like the pellets again. So the Lab 2 recovery test compares how the residue dissolves, whether it fizzes with vinegar and whether it clouds baking soda solution, not temperature, and in this course the hydrate still counts as calcium chloride recovered.
• 'Entirely different properties' (pp. 154, 161): products differ from reactants in at least some characteristic properties, not all. The book's own aspirin example (p. 159) shows a product that matches its reactant in color and in measured density. Two different substances can even share a melting point, so agreeing tests make a stronger claim than one test alone.
• The aspirin example numbers (p. 159) are the book's idealized teaching data. Reference values: salicylic acid melts at about 158-159 °C, dissolves about 2.2 g per liter of water at 25 °C and has a density near 1.44 g/cm³; aspirin melts at about 135 °C, dissolves roughly 3 to 4.6 g per liter at 25 °C depending on the source, and has a density of about 1.35-1.40 g/cm³. A packed powder contains air, so a measured 1.4 g/cm³ for a packed cube would read low in practice. A solubility comparison only means something if both measurements are at the same temperature.
• Melting point and purity (p. 159): a melting point 23 °C lower could in principle come from an impure sample, because impurities lower and widen the melting range. A pure substance melts over a narrow range of about a degree or two. The slide task has students ask for the melting range, not just the temperature.
• Physical versus chemical properties (p. 155): the printed sentence is garbled and says flammability is noticed only while a substance is burning. Use these definitions: a physical property can be observed or measured without the substance becoming a different substance; a chemical property describes whether and how the substance can change into new substances (flammability, reacting with an acid), so it is found by trying the reaction.
• Lead iodide (p. 155) is described as not soluble in water. It is very slightly soluble, about 0.08 g per 100 mL at 20 °C, which is why nearly all of it drops out as the yellow solid. Lead compounds are toxic; this reaction is described only and must not be done in class.
• Nitrogen dioxide and dinitrogen tetroxide (pp. 156-157): in a sealed tube the two gases are present together, and cooling shifts the mixture toward the colorless gas rather than converting all of it, which is why a cold tube can keep a faint yellow tint. Both gases are toxic to breathe; describe only. The word equilibrium is not required of students.
• Heated sugar (p. 158): the caption says the sugar is burned while the text describes heating it until it turns to caramel. Caramelizing by heating and burning in air are different processes, and caramel is not made of crystals. Say 'heated until it browns' and do not treat caramel's taste as evidence; nothing in a lab is tasted.
• PS1.B wording on p. 153 says atoms regroup into different molecules. Several substances in this lesson, such as sodium acetate and potassium nitrate, are ionic compounds made of ions rather than separate molecules. Say 'new substances' or 'new combinations of atoms' rather than molecules unless the substance really is molecular (carbon dioxide, water).
• Aspirin history (pp. 160-161): salicin was isolated from willow bark by the French pharmacist Henri Leroux in 1829 (the book says 1826); salicylic acid was made from salicin by Raffaele Piria in 1838; Charles Gerhardt first made acetylsalicylic acid in 1853; Felix Hoffmann made it in pure form at Bayer in 1897. Bayer's German patent application was refused and a U.S. patent ran from 1900, and some historians credit Arthur Eichengrün's role, so do not assess who patented aspirin or when. Felix Hoffmann was German.
• 'Clinical trials' in the 1800s (pp. 160-161): those patient tests lacked comparison groups, ethics review and other features of modern clinical trials, so say 'early patient tests' or 'the clinical trials of the time'. The book's 'no reports of dizziness or breathing problems' is a historical report, not a lasting difference: aspirin can irritate the stomach, cause bleeding and trigger breathing problems in some people, and doctors advise against routine use in children and teens. Never give dosing or medical advice; the chapter evaluates a design, not a treatment.
• The yeast station: yeast is not a reactant. It contains the enzyme catalase, which speeds the breakdown of hydrogen peroxide into water and oxygen gas while remaining unchanged. The reactant that is used up is the hydrogen peroxide.
• The steel wool station: iron reacting with oxygen and water forms rust (hydrated iron oxides); vinegar removes the protective coating on the fibers and 3% hydrogen peroxide supplies oxygen quickly, which is why the change is fast and warm. The orange product is crumbly and is not attracted to a magnet the way steel wool is. Steel wool itself is flammable; keep it away from any heat source and never use a flame in this chapter.
• Mass lost in Lab 3 is the carbon dioxide that escaped. Some carbon dioxide stays dissolved in the liquid, so measured losses run a little below the theoretical values given in the key, and household vinegar varies between about 4% and 6% acetic acid, which shifts the plateau. Treat the numbers as expected ranges, not targets. Conservation of mass is Lesson 13's job; here the point is that the gas has mass and that the output stops growing when a reactant runs out.
• The book says you cannot always tell a reaction happened by looking and mentions the scanning tunneling microscope (p. 153). Chemists do not normally confirm reactions with an STM; they compare properties, which is exactly what this lesson goes on to teach.