SC.8.P.8.1

Explore the scientific theory of atoms (also known as atomic theory) by using models to explain the motion of particles in solids, liquids, and gases.
General Information
Subject Area: Science
Grade: 8
Body of Knowledge: Physical Science
Idea: Level 2: Basic Application of Skills & Concepts
Big Idea: Properties of Matter - A. All objects and substances in the world are made of matter. Matter has two fundamental properties: matter takes up space and matter has mass which gives it inertia.

B. Objects and substances can be classified by their physical and chemical properties. Mass is the amount of matter (or "stuff") in an object. Weight, on the other hand, is the measure of force of attraction (gravitational force) between an object and Earth.

The concepts of mass and weight are complicated and potentially confusing to elementary students. Hence, the more familiar term of "weight" is recommended for use to stand for both mass and weight in grades K-5. By grades 6-8, students are expected to understand the distinction between mass and weight, and use them appropriately.

Clarification for grades K-2: The use of the more familiar term ‘weight’ instead of the term “mass” is recommended for grades K-2.

Clarification for grades 3-5: In grade 3, introduce the term mass as compared to the term weight. In grade 4, investigate the concept of weight versus mass of objects. In grade 5, discuss why mass (not weight) is used to compare properties of solids, liquids and gases.

Date Adopted or Revised: 02/08
Date of Last Rating: 05/08
Status: State Board Approved
Assessed: Yes

Related Courses

This benchmark is part of these courses.
2002100: M/J Comprehensive Science 3 (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
2002110: M/J Comprehensive Science 3, Advanced (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
2003010: M/J Physical Science (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
2003020: M/J Physical Science, Advanced (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
7820017: Access M/J Comprehensive Science 3 (Specifically in versions: 2014 - 2015, 2015 - 2018, 2018 and beyond (current))
2002055: M/J Comprehensive Science 1 Accelerated Honors (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
7920030: Fundamental Integrated Science 1 (Specifically in versions: 2013 - 2015, 2015 - 2017 (course terminated))

Related Access Points

Alternate version of this benchmark for students with significant cognitive disabilities.
SC.8.P.8.In.1: Compare properties of solids, liquids, and gases.
SC.8.P.8.Su.1: Recognize three states of matter, including solids, liquids, and gases.
SC.8.P.8.Pa.1: Recognize examples of the gaseous state of matter, such as steam or smoke.

Related Resources

Vetted resources educators can use to teach the concepts and skills in this benchmark.

Lesson Plans

States and Phases of Matter:

Students will collect and analyze data on the kinetic energy of molecules through the different states of matter. Throughout the lab, students will be modeling the process of adding and removing energy from matter which leads to phase changes. Students will use their knowledge of states of matter to introduce the relative amount of kinetic energy in each state of matter, how changes in the kinetic energy can causes phase changes in matter, and what those phase changes are called.

Type: Lesson Plan

Temperature and Particle Theory:

The resource allows students to model and describe how temperature affects molecular motion or particle theory.

Type: Lesson Plan

States of Matter:

States of matter seems like a simple concept. Everyone knows that water has a solid phase, which is ice, a liquid phase, which is water, and a gaseous stage, which is water vapor. At this level, students are expected to understand the motion of particles at the molecular level. A thorough understanding of particle motion is necessary in preparation for chemistry in the eight grade standards. This activity is fun at Halloween because families may use dry ice in Halloween displays.

Type: Lesson Plan

Particle Movement in Solids, Liquids, and Gases:

Using guided notes and an interactive game, students will be able to describe the motion of particles in solids, liquids, and gases.

Type: Lesson Plan

Alien Elements-Are they hiding here?:

This lesson is a high interest presentation and activity that presents the concepts of elemental composition, temperature effects, and states of matter geared to 8th graders.

Type: Lesson Plan

Atomic Theory:

The Purpose of the lesson is to teach the students about five major atomic theories using inquiry-based learning. By allowing the students to be introduced to the historical backgrounds and having each group to create a three dimensional figure and a poster, it allows the learning process to be student-driven, inductive and interactive.

Type: Lesson Plan

Gas Laws:

This is a "gold star" lesson plan that incorporates the virtual manipulative "Gas Properties" from PhET (University of Colorado). Students investigate properties of gases, represent predictions graphically, test predictions using the manipulative, and then extend the knowledge into real investigations (i.e. non virtual).

Type: Lesson Plan

It's Just a Phase: Water as a solid, liquid, and gas:

In this lesson, students use BBs to represent molecules and model water in the solid, liquid, and gaseous states. Background information for teachers is provided.

Type: Lesson Plan

The movement of particles in solids, liquids, and gases.:

Students will be able to describe the motion of the particles in solids, liquids, and gases.

Content statements:
- The particles of a gas move quickly and are able to spread apart from one another.
- The particles of a liquid are able to move past each other.
- The particles of a solid are not able to move out of their positions relative to one another, but do have small vibrational movements.

Type: Lesson Plan

Original Student Tutorial

Your Ice Cream Is Moving:

Learn to sequence a series of diagrams to create a model of a substance transitioning from a solid state to a liquid state in this interactive tutorial.

Type: Original Student Tutorial

Teaching Idea

What causes pressure?:

This demonstration has students model pressure at the atomic scale. Students are molecules, bouncing off the walls of a container (roped in area) to represent pressure. The students change their speed, to demonstrate changing temperature, and show that pressure increases as temperature increases. Students can be added to the simulation to show density changes.

Type: Teaching Idea

Unit/Lesson Sequences

Middle School Chemistry Unit | Chapter 2 | Changes of State:

Students help design experiments to test whether the temperature of water affects the rate of evaporation and whether the temperature of water vapor affects the rate of condensation. Students look in detail at the water molecule to explain the state changes of water.

Type: Unit/Lesson Sequence

Middle School Chemistry Unit | Chapter 1 | Matter—Solids, Liquids, and Gases:

Students are introduced to the idea that matter is composed of atoms and molecules that are attracted to each other and in constant motion. Students explore the attractions and motion of atoms and molecules as they experiment with and observe the heating and cooling of a solid, liquid, and gas.

Type: Unit/Lesson Sequence

Virtual Manipulatives

States of Matter: Basics:

This simulation will allow you to heat, cool and compress atoms and molecules and watch as they change between solid, liquid and gas phase.
Ideas to investigate:

  • Describe characteristics of three states of matter: solid, liquid and gas.
  • Predict how varying the temperature or pressure changes the behavior of particles.
  • Compare particles in the three different phases.
  • Explain freezing and melting with molecular level detail.
  • Recognize that different substances have different properties, including melting, freezing and boiling temperatures.

Type: Virtual Manipulative

Gas Properties:


Students will pump gas molecules to a box and see what happens as they change the volume, add or remove heat, change gravity, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

  • Students can predict how changing a variable among pressure, volume, temperature and number influences other gas properties.
  • Students can predict how changing temperature will affect the speed of molecules.
  • Students can rank the speed of molecules in thermal equilibrium based on the relative masses of molecules.

Type: Virtual Manipulative

Understanding solutions:

•Use pictures and proportional reasoning to explain changes in concentration
•Draw what happens at the molecular level when compounds dissolve in water
•Identify if a compound is a salt or sugar by macroscopic observations or microscopic representations.
•Explain how using combinations of solutes changes solution characteristics or not.
•Use observations to explain ways concentration of a solute can change.
•Describe ways the formula, macroscopic observations, or microscopic representations of a compound indicates if the bonding is ionic or covalent.

Type: Virtual Manipulative

PhET Gas Properties:

This virtual manipulative allows you to investigate various aspects of gases through virtual experimentation. From the site: Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, change gravity, and more (open the box, change the molecular weight of the molecule). Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

Type: Virtual Manipulative

Original Student Tutorials Science - Grades K-8

Your Ice Cream Is Moving:

Learn to sequence a series of diagrams to create a model of a substance transitioning from a solid state to a liquid state in this interactive tutorial.

Student Resources

Vetted resources students can use to learn the concepts and skills in this benchmark.

Original Student Tutorial

Your Ice Cream Is Moving:

Learn to sequence a series of diagrams to create a model of a substance transitioning from a solid state to a liquid state in this interactive tutorial.

Type: Original Student Tutorial

Virtual Manipulatives

States of Matter: Basics:

This simulation will allow you to heat, cool and compress atoms and molecules and watch as they change between solid, liquid and gas phase.
Ideas to investigate:

  • Describe characteristics of three states of matter: solid, liquid and gas.
  • Predict how varying the temperature or pressure changes the behavior of particles.
  • Compare particles in the three different phases.
  • Explain freezing and melting with molecular level detail.
  • Recognize that different substances have different properties, including melting, freezing and boiling temperatures.

Type: Virtual Manipulative

Gas Properties:


Students will pump gas molecules to a box and see what happens as they change the volume, add or remove heat, change gravity, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

  • Students can predict how changing a variable among pressure, volume, temperature and number influences other gas properties.
  • Students can predict how changing temperature will affect the speed of molecules.
  • Students can rank the speed of molecules in thermal equilibrium based on the relative masses of molecules.

Type: Virtual Manipulative

PhET Gas Properties:

This virtual manipulative allows you to investigate various aspects of gases through virtual experimentation. From the site: Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, change gravity, and more (open the box, change the molecular weight of the molecule). Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

Type: Virtual Manipulative

Parent Resources

Vetted resources caregivers can use to help students learn the concepts and skills in this benchmark.

Virtual Manipulatives

States of Matter: Basics:

This simulation will allow you to heat, cool and compress atoms and molecules and watch as they change between solid, liquid and gas phase.
Ideas to investigate:

  • Describe characteristics of three states of matter: solid, liquid and gas.
  • Predict how varying the temperature or pressure changes the behavior of particles.
  • Compare particles in the three different phases.
  • Explain freezing and melting with molecular level detail.
  • Recognize that different substances have different properties, including melting, freezing and boiling temperatures.

Type: Virtual Manipulative

Gas Properties:


Students will pump gas molecules to a box and see what happens as they change the volume, add or remove heat, change gravity, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

  • Students can predict how changing a variable among pressure, volume, temperature and number influences other gas properties.
  • Students can predict how changing temperature will affect the speed of molecules.
  • Students can rank the speed of molecules in thermal equilibrium based on the relative masses of molecules.

Type: Virtual Manipulative

Understanding solutions:

•Use pictures and proportional reasoning to explain changes in concentration
•Draw what happens at the molecular level when compounds dissolve in water
•Identify if a compound is a salt or sugar by macroscopic observations or microscopic representations.
•Explain how using combinations of solutes changes solution characteristics or not.
•Use observations to explain ways concentration of a solute can change.
•Describe ways the formula, macroscopic observations, or microscopic representations of a compound indicates if the bonding is ionic or covalent.

Type: Virtual Manipulative

PhET Gas Properties:

This virtual manipulative allows you to investigate various aspects of gases through virtual experimentation. From the site: Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, change gravity, and more (open the box, change the molecular weight of the molecule). Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

Type: Virtual Manipulative