Unit 08 · Electrochemistry & Redox
The year closes with the chemistry of electron transfer. This unit covers assigning oxidation states, identifying what is oxidized and what is reduced, balancing redox equations by half-reactions, and building the two kinds of electrochemical cells — galvanic cells that turn a reaction into a voltage, and electrolytic cells that use a voltage to force a reaction. Mastery means you can trace electrons from one species to another and build a working cell.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Oxidation states | Cannot assign an oxidation number. | Assigns states for simple ions but errs in compounds. | Assigns oxidation states reliably and uses changes to identify what is oxidized and reduced. |
| Identifying oxidation & reduction | Mixes up which species gains and loses electrons. | Names oxidation and reduction but confuses oxidizing and reducing agents. | Distinguishes oxidation, reduction, and the agents driving each in any reaction. |
| Balancing redox equations | Balances atoms but ignores charge and electrons. | Writes half-reactions but cannot reconcile electrons or add H⁺/OH⁻. | Balances redox equations by half-reactions in acidic or basic solution, conserving mass and charge. |
| Galvanic & electrolytic cells | Cannot tell the two cell types apart. | Labels electrodes but confuses anode, cathode, or electron flow. | Distinguishes the cells, identifies the anode and cathode, and predicts cell voltage or required potential. |
| Lab technique (building a cell) | Cannot assemble a functioning cell. | Builds a cell but with reversed electrodes or a missing salt bridge. | Constructs a working galvanic or electrolytic cell and measures or drives the expected reaction. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“Zinc loses electrons, so it’s oxidized and it’s the anode; the copper ion gains them at the cathode. I assigned oxidation states to see what actually changed, then balanced the electrons before the atoms.”
“Redox is reduction and oxidation together. The metal does something with electrons. I’d have to guess which side is the anode.”
You demonstrate this unit by building a galvanic cell — or running an electrolysis — measuring its voltage or product and explaining the electron flow aloud, not on a multiple-choice test. A criterion counts as mastered only when your cell works as predicted and you can justify the redox chemistry behind it. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.