Middle school · Science · 20 minutes
Particles, Physical Changes and Chemical Changes
Use particle models and evidence to distinguish types of material change.
Middle School Science Foundations · Lesson 2 · Starter collectionLearning objective
Use particle models and evidence to distinguish types of material change.
Gather your materials
- Paper or a shared note-taking document
- The original passage, example or data provided in this lesson
The lesson time covers the core activity. Allow extra time for video viewing and extended discussion.
Supporting Common Core connection
SL.6.1Standard level: Grade 6
Prepare evidence, share roles, ask questions and explain how a discussion changes or strengthens your conclusion.
Read the official standard ↗This connection applies to the structured discussion below. It does not establish alignment with science or social studies content standards. Code and level checked 2026-11-04; selected skill coverage.
Teach it step by step
- Ask what the learner already knows. Introduce the objective and read the explanation together.
- Work through the example aloud. Pause for the learner to explain why each step or piece of evidence matters.
- Choose a video if useful, then connect it to the example. Let the learner complete the independent practice before checking the explained answers.
- Discuss the question below and finish with the exit check. Revisit the example if the reasoning is unclear.
Watch, notice, discuss
Video choices for this lesson
Preview a video, then choose what fits your learners. “Show to class” opens a larger view; use the player’s play and full-screen controls when you’re ready.
Teacher preview needed. Check the language, level and length before showing. YouTube may show ads or related videos.
Chemical changes | Middle school chemistry | Khan Academy
By Khan Academy
Use this explanation as an introduction, then pause to connect it to the worked example and discussion question.
Open on YouTube: Chemical changes | Middle school chemistry | Khan Academy (opens a new tab) ↗Physical and Chemical Changes: Chemistry for Kids - FreeSchool
By Free School
Compare this alternate explanation with the lesson. Ask learners to show their reasoning after watching.
Open on YouTube: Physical and Chemical Changes: Chemistry for Kids - FreeSchool (opens a new tab) ↗What evidence would distinguish a new substance from a change in state? Explain a limit of your observation.
An external player loads only after you choose Preview or Show to class. Playback connects to YouTube. Videos belong to their creators; availability and embedding can change.
Understand the idea
Matter is made of particles. In a physical change, a substance changes form or state without becoming a different substance. In a chemical change, atoms are rearranged into different substances. Melting ice changes the arrangement and motion of water particles; water remains water. Evidence such as a new gas or an unexpected temperature change may support a chemical-change explanation, but one sign alone is not always decisive.
Worked example
An ice cube melts into liquid water: a physical change. Iron gradually forms rust by reacting with oxygen and moisture: a chemical change that produces iron oxides. Bubbles in boiling water are water vapor, so bubbles do not automatically mean a chemical reaction. Use the substance and context to explain the observation. This is a model-and-observation lesson; no mixing or heating is needed.
Try it yourself
- Classify tearing paper and explain your choice.
- Why is rusting different from melting?
- Why are bubbles alone insufficient evidence of a chemical change?
Check your reasoning
- Physical change: the pieces are still paper, although their size and shape changed.
- Rusting produces different substances; melting changes state while the substance remains the same.
- Boiling can form bubbles through a physical state change. More information about the substances and conditions is needed.
Make it work for your learner
For support, model the example one step at a time and ask the learner to explain each choice in their own words. Use a sketch, organizer or physical model where helpful. For a challenge, create a new example, test an alternative explanation or describe when the model would not apply.
Exit check
Use particle models and evidence to distinguish types of material change. Explain your reasoning with a specific example before moving on.
Prepare · Discuss · Reflect
Use evidence in a conversation
Discussion question: What evidence would distinguish a new substance from a change in state? Explain a limit of your observation.
- Before discussing, write a tentative answer with two details from the lesson’s passage, example or data. For a longer discussion, the teacher can add an age-appropriate source.
- In pairs, a group or a tutor–learner conversation, agree on roles: facilitator, evidence finder and note taker. Combine roles when needed and allow equal time to respond.
- Share evidence, ask a clarifying question and respond to a different interpretation. Explain which details support or challenge a claim.
- Paraphrase another person’s point. Write a final conclusion explaining what changed, what remains uncertain and what evidence you would seek next.
Teacher look-for: Accurate use of the example, reasons linked to evidence, thoughtful questions and a response to another viewpoint. A well-supported alternative answer is welcome.