Unit Plan 25 (Grade 8 Science): Energy & Particle Models

Focus: Connect particle motion, temperature, state of matter, and energy transfer by modeling how adding or removing thermal energy changes the average kinetic energy of particles and can cause phase changes in different materials.

Grade Level: 8

Subject Area: Science (Physical Science • Matter & Its Interactions • Energy)

Total Unit Duration: 5 sessions (one week), 50–60 minutes per session

I. Introduction

Students synthesize their understanding of particles, thermal energy, and energy transfer across solids, liquids, and gases. They use particle diagrams and energy bar models to show how temperature reflects the average kinetic energy of particles, and how adding or removing energy can change particle motion and sometimes state (melting, freezing, boiling, condensing). Through a guided investigation, students examine how mass and type of matter affect temperature change when energy is transferred, then connect their data to particle-level explanations. By the end of the week, they can explain both what happens that we can measure (temperature changes, phase changes) and what happens that we can’t see (particles speeding up, slowing down, rearranging).

Essential Questions

• How does temperature relate to the average kinetic energy of particles in a substance?
• What happens to particle motion and arrangement when thermal energy is added or removed from solids, liquids, and gases?
• How do mass and type of matter affect how much the temperature changes when the same amount of energy is transferred?
• How can particle models and energy-transfer investigations work together to explain heating, cooling, and changes of state?
• Why is it important to understand particle and energy models when thinking about real-world problems (cooking, weather, climate, materials)?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Explain that temperature is related to the average kinetic energy of particles, not how many particles there are or how big they are.
2. Use particle diagrams to compare solids, liquids, and gases, showing differences in spacing, motion, and arrangement.
3. Plan and conduct an investigation to explore how type of matter and mass affect temperature change when thermal energy is transferred (e.g., heating or cooling).
4. Analyze and interpret temperature data from their investigation to describe relationships among energy transfer, type of matter, mass, and change in average kinetic energy of particles.
5. Develop and use models (particle diagrams, heating/cooling curves, bar models) to predict and describe how particles’ motion, temperature, and state change when thermal energy is added or removed.
6. Construct written or oral explanations that link macroscopic measurements (temperature, state) to microscopic particle behavior and energy transfer.

Standards Alignment — 8th Grade (NGSS-based custom)

• MS-PS3-4 — Plan and conduct an investigation to determine the relationships among energy transfer, type of matter, mass, and change in average kinetic energy of the particles (observed as temperature change).
  • In this unit, students design and carry out a heating/cooling investigation with different materials and masses, measuring temperature change and connecting results to average kinetic energy.
• MS-PS1-4 (spiral) — Develop a model that predicts and describes changes in particle motion, temperature, and state when thermal energy is added or removed.
  • In this unit, students revisit and deepen particle models of solids, liquids, and gases and apply them to phase changes and heating/cooling curves.

Success Criteria — Student Language

• I can explain how temperature is related to the average kinetic energy of particles in a substance.
• I can draw particle models for solids, liquids, and gases, and show what changes when a substance is heated or cooled.
• I can help plan and carry out an investigation that tests how type of matter and mass affect temperature change when energy is transferred.
• I can use data (tables, graphs) to describe relationships between energy transfer, mass, material, and temperature change.
• I can use models (particle diagrams, bar models, heating/cooling curves) to describe and predict changes in particle motion, temperature, and state when thermal energy is added or removed.