Physical Science · California Grade 7
MS-PS1-1
Develop models to describe the atomic composition of simple molecules and extended structures.
Clarification statement: Emphasis is on developing models of molecules that vary in complexity. Examples of simple molecules could include ammonia and methanol. Examples of extended structures could include sodium chloride or diamonds. Examples of molecular-level models could include drawings, 3D ball and stick structures, or computer representations showing different molecules with different types of atoms.
Assessment boundary: Assessment does not include valence electrons and bonding energy, discussing the ionic nature of subunits of complex structures, or a complete description of all individual atoms in a complex molecule or extended structure is not required.
Chapters
Chapter 1: Atoms and Elementspractice
This lesson establishes that substances are made of different kinds of atoms and introduces the periodic table as the catalog of those kinds. Students build and use models of atomic scale and of the table, which prepares them to model molecules and extended structures in Lesson 2; no slide or task here asks for a molecule model, so the role is practice, not assesses.
This is the lesson's home standard. Students build gumdrop models of water, oxygen, carbon dioxide, methane, ammonia and the butane/isobutane pair (Lab 1), draw and label molecule and lattice models (W4, W10), and model table salt and a polymer chain as repeating structures. The assessment boundary is respected: no valence electrons, no bond energies, and the charged nature of salt's particles is mentioned only as a teacher note.
The lesson opens by presenting a substance as a visible-scale quantity of one kind of molecule or extended structure, which connects the models students built in Lesson 2 to the samples they can hold and measure here. No new molecule models are developed, so this is background support.
Worksheets (22)
| Chapter | Worksheet | Role | How it connects |
|---|---|---|---|
| Ch. 1 | W1 · The Ball That Got Heavier: Is Air Something? Phenomenon exploration | supports | Before students can model molecules made of atoms, they need to accept that invisible gases are matter made of particles with mass. This phenomenon builds that foundation; it does not yet produce evidence toward the molecular models the PE asks for. |
| Ch. 1 | W2 · Atom, Element, Table: Words That Fit Together Vocabulary in action | supports | Modeling the atomic composition of molecules requires a firm grip on what an atom is, what an element is, and how the periodic table names them. This sheet builds that language; it is background for the PE rather than evidence of it. |
| Ch. 1 | W3 · Sorting the Invisible: How the Periodic Table Was Built Reading with evidence | supports | The periodic table is the tool students will use to name the atoms in every molecular model they build for this PE. This reading gives the history and logic behind that tool; it is background rather than evidence toward the PE. |
| Ch. 1 | W4 · Reading a Slice of the Periodic Table Diagrams and models | practice | Students practice the modeling skill the PE depends on (representing atoms by symbol and reading them from the table) but with single elements rather than molecules, so this builds toward the PE without assessing it. |
| Ch. 1 | W5 · Grams per Stroke and the Halfway Rule: Two Datasets Data and graphing | supports | Analyzing the mass added by invisible air and the regular pattern of atomic masses gives students quantitative reasons to believe that matter is made of particles with mass, the idea beneath every molecular model in this PE. |
| Ch. 1 | W6 · Which Element Is Sample X? A Claim-Evidence-Reasoning Case Claim, evidence, reasoning | practice | Identifying an element from its atomic mass and group behavior exercises the periodic-table reasoning that students will need when they label the atoms in molecular models; it builds toward the PE without producing a model of a molecule. |
| Ch. 1 | W7 · Fixing Priya's Notebook: Six Mistakes About Atoms and Elements Error analysis | supports | Students who confuse atom with element, or think invisible gases are not matter, build molecular models that are wrong in their basic parts. Clearing these errors prepares students for the PE's modeling work. |
| Ch. 1 | W8 · Build the Table, Defend the Blank: An Element Jigsaw Collaborative investigation | practice | Sorting elements by behavior and mass rebuilds the logic of the periodic table that students rely on when they choose and label atoms in molecular models; it builds the practice of using patterns without yet modeling molecules. |
| Ch. 1 | W9 · Design Challenge: A Hallway Model of the Atomic Scale Transfer and design | supports | Reasoning about how far atoms are from everyday sizes is background for modeling molecules and extended structures; the challenge does not produce a molecular model. |
| Ch. 1 | W10 · Atoms and Elements: Mastery Check Retrieval and mastery check | supports | This quiz checks the prerequisite ideas (atoms as particles of elements, symbols and masses from the table) that the PE's molecular models are built from; it does not ask students to model a molecule. |
| Ch. 2 | W1 · Pencil Core and Saw Blade: Two Solids Made of the Same Atoms Phenomenon exploration | supports | This sheet surfaces the puzzle that the PE's models will solve: the same atoms, connected in different patterns, make different materials. Students only observe and explain in words here; the model-building comes in later worksheets. |
| Ch. 2 | W2 · Molecule, Structure, Ratio: Words for How Atoms Join Vocabulary in action | supports | The PE asks students to model the atomic composition of molecules and extended structures. This sheet builds the vocabulary those models must be labeled with, especially the difference between an exact count (molecule) and a constant ratio (extended structure). |
| Ch. 2 | W3 · The Salt That Had No Molecules: How X-rays Revealed Extended Structures Reading with evidence | practice | Students read how the models of sodium chloride, diamond and graphite were established and describe each arrangement in their own words. Describing these arrangements accurately is the thinking they will need when they draw the models themselves in Worksheets 4 and 9. |
| Ch. 2 | W4 · Reading Models, Building Models: Molecules and a Salt Slice Diagrams and models | assesses | Part B asks students to develop ball-and-stick models of butane and isobutane that show composition and structure, which is direct evidence toward the PE. Part A has them read the composition of molecules and of a salt slice and a polymer chain from given models. Bonding energy, charges and the complete atom-by-atom description of large structures are not required, in line with the assessment boundary. |
| Ch. 2 | W5 · Counting Atoms in Fragments: Why a Crystal Has a Ratio, Not a Count Data and graphing | practice | Students analyze atom counts to discover why the composition of an extended structure is written as a ratio and the composition of a molecule as an exact count. This is the quantitative reasoning behind the labels on the models the PE asks for, practiced with data rather than by drawing. |
| Ch. 2 | W6 · Why Does One Carbon Write and the Other Cut? A CER Case Claim, evidence, reasoning | practice | Students read models of diamond and graphite and use them, with test data, to explain why the two pure-carbon solids behave differently. This exercises the crosscutting idea that macroscopic patterns come from atomic-level structure, which the lesson's final section builds toward, without requiring students to draw the models here. |
| Ch. 2 | W7 · Checking Dani's Study Guide: Eight Claims About Molecules and Crystals Error analysis | practice | Each error targets a mistaken idea that shows up in student models for this PE: treating salt as a molecule, ignoring structure, reading model colors as real, or confusing a ratio with a count. Diagnosing and rewriting the statements strengthens the ideas students will put into their own models. |
| Ch. 2 | W8 · Twelve Substances, Four Columns: A Molecule and Structure Jigsaw Collaborative investigation | practice | Students describe the atomic composition and structure of twelve substances and sort them into molecules and kinds of extended structures. Describing and comparing these models in words builds the understanding they need to develop their own models; the sheet does not itself require a drawn model. |
| Ch. 2 | W9 · Design Brief: A Touchable Salt-Crystal Model for Science Night Transfer and design | assesses | The product is a model of sodium chloride that must show its repeating pattern, its 1:1 ratio and the absence of a smallest particle. Deciding what a correct model must show, and sketching it, is direct evidence toward developing models of extended structures. Charges on the particles are not required, in line with the assessment boundary. |
| Ch. 2 | W10 · Molecules and Extended Structures: Mastery Check Retrieval and mastery check | assesses | Items ask students to read compositions from formulas, identify molecules and extended structures, draw a ball-and-stick model of ammonia, and explain why an extended structure's composition is a ratio. Together they produce evidence toward the PE within its assessment boundary: no charges, bonding energies or complete descriptions of large structures are required. |
| Ch. 3 | W1 · The Jar That Sorts Things: Five Liquids, Four Objects Phenomenon exploration | supports | Background link: the liquids and objects in the jar are macroscopic samples of molecules and extended structures that students modeled in the previous chapters. Students connect the visible layers to the invisible particles they are made of. |
| Ch. 13 | W4 · Count Before, Count After: Modeling a Reaction with Atoms Diagrams and models | supports | Drawing water, hydrogen and oxygen as groups of labeled atoms uses the molecular-model skill from earlier in the unit; it is a tool here, not the thing being assessed. |
Labs (7)
| Chapter | Lab | Role | How it connects |
|---|---|---|---|
| Ch. 1 | Lab 1 · Halving to the Atom: How Many Cuts to the Bottom? Physical model | practice | Students build a quantitative sense of the atomic scale and of the atom as the smallest unit of an element, which they need before they can develop models of molecules and extended structures in Lesson 2. |
| Ch. 1 | Lab 2 · The Mystery Element Cards: Build a Table That Predicts Evidence-based mystery | practice | Students build and use the periodic arrangement as a model that organizes the kinds of atoms by properties and mass and makes testable predictions, the organizing idea they rely on when modeling molecules and extended structures in Lesson 2. |
| Ch. 1 | Lab 3 · Design a Touch Microscope: Map a Surface You Cannot See Engineering design challenge | supports | The shoebox probe is an analogy for the STM, which maps the atoms on a surface; the lab supports the idea that atoms are real, countable objects on a surface without assessing molecule models. |
| Ch. 2 | Lab 1 · Count or Ratio? Building Molecules and a Salt Block Physical model | assesses | Students develop physical models of water, oxygen, carbon dioxide, methane, ammonia, hydrogen peroxide, butane, isobutane and a sodium chloride block, record each model's composition, and explain the count-versus-ratio difference. This is direct evidence toward the PE within its boundary: no electrons, bond energies or ionic charges are involved. |
| Ch. 2 | Lab 2 · Which Structure Is It, and Which Job Can It Do? Data-driven decision | practice | Students do not build models here; they use written structure models and fragment-count data to describe each solid's composition (fixed count or fixed ratio) and connect structure to what they observe. That builds the modeling practice and the PS1.A idea that solids may be molecules or extended structures, without producing a full model of their own. |
| Ch. 2 | Lab 3 · Sheets or Networks: Build a Structure That Survives Engineering design challenge | practice | The reference builds are physical models of the two carbon structures, and the design phase keeps the 'limited connections per atom' rule, so students are modeling extended structures while they engineer. It is practice rather than assessment because the design tower is not a model of any particular substance. |
| Ch. 13 | Lab 2 · Beads Never Vanish: Build Four Reactions and Catch the Fakes Physical model | supports | Students built bead and drawn models of molecules in Lesson 2; this lab reuses that skill so the focus can stay on what changes and what does not when molecules regroup. |