Physical Science · California Grade 7

MS-PS1-4

Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

Clarification statement: Emphasis is on qualitative molecular-level models of solids, liquids, and gases to show that adding or removing thermal energy increases or decreases kinetic energy of the particles until a change of state occurs. Examples of models could include drawings and diagrams. Examples of particles could include molecules or inert atoms. Examples of pure substances could include water, carbon dioxide, and helium.

Source: California Department of Education, NGSS Preferred Integrated Course Model, Grade 7 (accessed 2026-10-18)

Chapters

Chapter 23: The Motion of Particlesassesses

Every strand of this chapter builds or uses a particle model of solids, liquids and gases. Lab 2 and Lab 3 have students run a model in which adding or removing energy changes particle motion and then the state, and record the result as data; W4, W6 and W9 ask for drawn and written models that predict what happens when a pure substance is heated or cooled. No task asks for a calculation of energy or heat.

Chapter 24: Heat, Temperature, and State Changesassesses

Students build and use particle models of solids, liquids and gases for all six state changes, and in Lab 1 they predict, measure and model a melting curve, drawing what the particles are doing before, during and after melting and explaining why the temperature holds at 0 °C. The chapter stays inside the clarification statement: models are drawings and diagrams, and no task calculates energy.

Worksheets (20)

Chapter	Worksheet	Role	How it connects
Ch. 23	W1 · One Drop, Two Glasses: Why Does Dye Spread Faster in Warm Water? Phenomenon exploration	supports	Watching dye spread at two temperatures is the entry phenomenon for the idea that particles in every state move and that warmer samples have faster-moving particles. Students only record and explain here; the model-building that the PE asks for comes later in the chapter.
Ch. 23	W2 · One Particle or Many? Connecting the Words for States and Motion Vocabulary in action	supports	A particle model of heating and cooling only works if students keep two levels apart: what one particle has (size, mass, speed) and what a whole sample has (temperature, state, pressure, melting and boiling points). This sheet builds that vocabulary before students draw and use models in W4, W6 and W9.
Ch. 23	W3 · The Jiggle That Would Not Stop: Reading the Evidence for Moving Particles Reading with evidence	practice	The passage builds the motion half of the particle model: particles in every state are always moving, and a higher temperature means faster average motion. Students cite evidence and use it to predict what cooling or warming does to particle motion, but they do not yet build the full heating-and-cooling model the PE asks for.
Ch. 23	W4 · Flat Steps on a Heating Curve: Drawing What the Particles Are Doing Diagrams and models	assesses	Students interpret a heating curve, draw a three-panel particle model of solid, liquid and gas water, and then predict and explain the cooling curve when energy is removed. That drawn, explained model is the evidence the PE asks for. No energy or heat quantities are calculated.
Ch. 23	W5 · Timing the Spread: Dye, Temperature and the Shape of the Curve Data and graphing	practice	Students analyze data showing that dye spreads faster in warmer water, then use a gel test that removes currents to isolate diffusion. Explaining the pattern with faster average particle motion practices the motion-and-temperature part of the PE; no change of state is modeled here.
Ch. 23	W6 · Mercury or Alcohol? A Claim-Evidence-Reasoning Case for a Polar Winter Claim, evidence, reasoning	assesses	The reasoning section requires a particle model that predicts what happens to mercury and ethanol as energy leaves them: slower average motion and falling temperature, then particles settling into fixed positions at a steady temperature while mercury freezes. That is the PE applied to cooling. Evidence comes from real melting points at 101 kPa and a cooling dataset; no energy is calculated.
Ch. 23	W7 · Fixing Theo's Kitchen Notes: Eight Claims About Particles and States Error analysis	practice	Diagnosing Theo's statements makes students state the particle model precisely: particles move in every state, keep their size during a change of state, and hold the temperature steady at the boiling point while energy is added. Students repair a model rather than build one from scratch, so this is practice toward the PE.
Ch. 23	W8 · Temperature or Pressure? A Twelve-Card Evidence Sort on Changing States Collaborative investigation	practice	Groups explain twelve real observations with particle motion and collisions and build water's boiling line from the cards, extending the heating-and-cooling model to include pressure. This practices the model the PE describes; the sheet does not ask for a full predictive model of adding or removing energy, so it is not used as PE evidence.
Ch. 23	W9 · Keep It Between 2 and 8: Choosing a Melting Pack for a Vaccine Cooler Transfer and design	assesses	Students predict, from melting points and the particle model, that a solid pack warms to its melting point and then holds that temperature while its particles leave their fixed positions, and they explain why more pack material holds longer and what happens once it has all melted. That prediction, applied to a new system, is evidence for the PE. No energy is calculated; the only arithmetic is cost.
Ch. 23	W10 · The Motion of Particles: Mastery Check Retrieval and mastery check	assesses	Items 1 to 4, 9 and 10 and the synthesis (item 12) ask students to use a particle model to predict and describe particle motion, temperature and state as thermal energy is added or removed, which is the PE as written. Items 5 to 8 cover pressure and how it shifts boiling points, from the same DCI. The only calculation is a pressure calculation; no energy is calculated.
Ch. 24	W1 · The Sweating Glass and the Stubborn Thermometer Phenomenon exploration	supports	Students observe water appearing on cold surfaces and a thermometer that holds at 0 °C while ice melts, and propose first explanations. The chapter's model of particles gaining or losing thermal energy and changing state will explain both; this sheet raises the questions but does not yet build or assess the model.
Ch. 24	W2 · Word Webs: Heat, Temperature, Thermal Energy and Six Changes of State Vocabulary in action	practice	Sorting the six changes by whether thermal energy is added or removed, and naming the change in new situations, builds the language students need to write the predictive particle model the PE asks for. Students do not draw the model on this sheet.
Ch. 24	W3 · The Thermometer That Stopped Climbing Reading with evidence	practice	The passage models what happens to particle motion, temperature and state as thermal energy is added to and removed from water, and the questions ask students to restate that model with evidence. Students explain rather than build their own model here; W4 asks them to draw it.
Ch. 24	W4 · Reading a Heating Curve and Drawing What the Particles Do Diagrams and models	assesses	Students build qualitative molecular-level drawings for four moments on a heating curve and predict a cooling curve, which is the kind of model the clarification statement describes. Water is the pure substance; no step asks for an amount of energy.
Ch. 24	W5 · Twice the Ice: What Changes When the Sample Is Bigger? Data and graphing	practice	Students use graphed data to describe when the temperature of water rises and when it holds steady during melting and boiling, then explain the pattern with particles. This builds the evidence base for the predictive model the PE asks for; the sheet analyzes data rather than having students construct the model.
Ch. 24	W6 · Case Closed? Where the Water on a Cold Can Comes From Claim, evidence, reasoning	assesses	The reasoning section requires students to describe how water vapor particles lose thermal energy to a colder surface, slow down and are held together by their attractions as a liquid, which is the PE's model applied to energy removal. The argument is qualitative; no part asks for an amount of energy.
Ch. 24	W7 · Fixing Jordan's Notebook: Heat, Cold and the Missing Flat Lines Error analysis	practice	Diagnosing Jordan's straight-line heating curve and his particle statements, then drawing the corrected curve, exercises exactly what the PE's model must get right: temperature holds steady during a change of state, particles do not change, and evaporation does not need the boiling point. Students repair a model rather than build one from scratch.
Ch. 24	W8 · Substance Experts: Why Each Substance Changes State at Its Own Temperature Collaborative investigation	practice	Groups use melting and boiling points to predict the state of twelve pure substances, including the examples the clarification statement names (water, carbon dioxide, helium), and explain the pattern with particle attractions. This practices the predictive side of the PE; the individual section checks each student's reasoning.
Ch. 24	W9 · Frost Night at Oak Hollow Vineyard: Choose the Protection Plan Transfer and design	assesses	Students must predict and explain, with particles, why water that keeps freezing on a bud holds it near 0 °C, why the bud chills once the water stops, and why too little water fails. That is the PE's predictive model applied in a new setting. No step calculates energy; the only arithmetic is water volume.
Ch. 24	W10 · Heat, Temperature and State Changes: Mastery Check Retrieval and mastery check	assesses	Items 4, 5, 7 and 12 ask students to predict and describe particle motion, temperature and state for pure substances gaining or losing thermal energy, including a drawn particle model and a heating-curve story for a new substance. All items are qualitative or read temperatures and times; none calculates energy.

Labs (6)

Chapter	Lab	Role	How it connects
Ch. 23	Lab 1 · The Three-Cup Mystery: Rank the Temperatures by Watching Dye Evidence-based mystery	practice	Students use dye spreading as evidence that particles in still water are always moving and move faster on average when the water is warmer, one link in the PE's model of particle motion and temperature. No energy is added or removed to change a state, so the lab builds toward the PE rather than assessing it.
Ch. 23	Lab 2 · The Marble Tray: Shake In Energy, Watch the State Change Physical model	assesses	Students run a physical model in which adding energy (harder shaking) changes the particles' motion and arrangement from solid-like to liquid-like to gas-like and removing it reverses the change; the three-panel drawing and q4 to q7 produce qualitative evidence toward the PE. Part B adds the PS1.A idea that pressure comes from particle collisions. The model has no thermometer, so the temperature part of the PE is completed in Lab 3; no energy is calculated.
Ch. 23	Lab 3 · Energy Tokens: Act Out Melting and Boiling, Then Graph It Collaborative systems modeling	assesses	Students run a model in which each added unit of energy either raises particle motion, and so the temperature, or changes the state while the temperature holds, and they record and graph the result. The heating curve, the state counts and q4 to q9 are direct evidence toward the PE. Tokens are counted only to track where the energy goes; no energy or heat is calculated.
Ch. 24	Lab 1 · The Bath and the Melting Ice: Where Does the Energy Go? Collaborative systems modeling	assesses	Students predict the curve, measure it, and then develop a drawn particle model that describes what the particles are doing in each stretch and explains why the temperature holds at the melting point while the state changes. The drawing and the written explanations (q5, q6, drawing) are evidence for the PE, and no energy is calculated.
Ch. 24	Lab 2 · Which Cup Holds More Thermal Energy? The Four-Cup Ice Mystery Evidence-based mystery	practice	Students explain with particles why a larger, cooler cup can melt more ice than a smaller, hotter one, and why melting stops at 0 °C. This practices the particle reasoning of the PE; the full model of temperature and state over time is assessed in Lab 1.
Ch. 24	Lab 3 · Save the Ice Cube: Design, Test and Improve an Insulated Holder Engineering design challenge	supports	The lab rests on the chapter's model: the ice melts because energy flows into it from the warmer room, and it melts at 0 °C whatever the insulation (q10). Students use the model rather than develop it here.