• 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. (MS-PS1-4)

• Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as either motions of particles or energy stored in fields. (HS-PS3-2)

• Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. (6-8)
• In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. (6-8)
• The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter. (6-8)

• Phenomena that can be observed at one scale may not be observable at another scale. (6-8)
• The significance of a phenomenon is dependent on the scale, proportion, and quantity at which it occurs. (9-12)

• Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion). (6-8)

• Complex and microscopic structures and systems can be visualized, modeled, and used to describe how their function depends on the relationships among its parts, therefore complex natural structures/systems can be analyzed to determine how they function. (6-8)

• Constructing explanations and designing solutions in 6–8 builds on K–5 experiences and progresses to include constructing explanations and designing solutions supported by multiple sources of evidence consistent with scientific ideas, principles, and theories. (6-8)
  • Apply scientific ideas to construct an explanation for real-world phenomena, examples, or events. (6-8)

• Modeling in 6–8 builds on K–5 and progresses to developing, using and revising models to describe, test, and predict more abstract phenomena and design systems. (6-8)
  • Develop and use a model to describe phenomena. (6-8)
• Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. (9-12)
  • Use a model to provide mechanistic accounts of phenomena. (9-12)

• 6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
• 6-8: 4D/M3ab. Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated.
• 6-8: 4D/M3cd. In solids, the atoms or molecules are closely locked in position and can only vibrate. In liquids, they have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions.
• 6-8: 4D/M7a. No matter how substances within a closed system interact with one another, or how they combine or break apart, the total mass of the system remains the same.
• 6-8: 4D/M7b. The idea of atoms explains the conservation of matter: If the number of atoms stays the same no matter how the same atoms are rearranged, then their total mass stays the same.
• 6-8: 4D/M8. Most substances can exist as a solid, liquid, or gas depending on temperature.

• 6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.
• 6-8: 11B/M5. The usefulness of a model depends on how closely its behavior matches key aspects of what is being modeled. The only way to determine the usefulness of a model is to compare its behavior to the behavior of the real-world object, event, or process being modeled.

This resource explores a useful model for the structure of matter, designed to help novice learners visualize the structure of solids, liquids, and gases as matter composed of tiny particles in constant motion. The pacing of this animated tutorial allows it to be adaptable for middle school and high school.

• Physical Sciences K-8 Matter and Interactions Unit
• Physics First Matter and Interactions Unit
• Conceptual Physics Matter and Interactions Unit
• Algebra-Based Physics Matter and Interactions Unit

This resource explores a useful model for the structure of matter, designed to help novice learners visualize the structure of solids, liquids, and gases as matter composed of tiny particles in constant motion. The pacing of this animated tutorial allows it to be adaptable for middle school and high school.

• Physical Sciences K-8 Properties of Matter Unit
• Physics First Properties of Matter Unit
• Conceptual Physics Properties of Matter Unit
• Algebra-Based Physics Properties of Matter Unit