Physical vs Chemical Changes

ScienceMatter & MaterialsAges 11–13

Distinguish between physical changes (reversible, no new substances formed) and chemical changes (new substances formed, often irreversible), using conservation of mass to understand both types

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Teaching Table

Set out your lesson

Distinguish changes by substance identity and explain mass conservation using a defined system boundary.

Activity

Ask what an atom is, how a molecule differs from a single atom, and what would happen to a scale reading if matter left the weighed container. If unclear, revisit particle models and conservation before Try.

If Not Ready

Pause the fresh check. Revisit the named prerequisite or repeat the Show with smaller steps; record supported practice rather than an independent result. Authored predecessor existence never proves this learner is ready.

Allow 25–30 minutes with a break. This is entirely a paper/screen lesson: no chemicals, food, heat, flame, sealed containers or laboratory kit are needed. The atom diagrams and fictional data are supplied. Hide the worked diagrams during the fresh classification task; allow the learner to make their own sketch.

Paper/screen reasoning only. Do not burn toast, light gases, mix chemicals, heat liquids or seal a reacting container. The atom reaction and mass records are explanatory models, not procedures. Do not eat or taste materials for this lesson. A real conservation experiment involving gases or burning belongs in an appropriately equipped laboratory with qualified supervision; this packet does not provide that protocol.

Record the learner’s actual words or work, task ID and any help. Do not prefill success. Allow oral, pointing or written responses as appropriate; oral independent reasoning is not automatically supported. Copied/scribed text is not independent composition or handwriting. No name, account, upload or real family record is required.

Use the complete materials on screen or print only the current sheet. Keep adult guidance out of learner view. Retain an earlier model only when the current step supplies it as context.

Teaching limits and safe use

These are finite task opportunities, not proof of mastery. Record what was attempted and what support was used.

Reversibility alone is not a reliable test for distinguishing physical and chemical changes.
Laboratory performance, measurement uncertainty and real reaction observation are not assessed.
Finite task opportunities, not learner mastery or universal canonical coverage.
Use the supplied materials on screen or print one current sheet; physical printing can vary.
Record the actual response and assistance; completing a task does not establish mastery.

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Distinguish changes by substance identity and explain mass conservation using a defined system boundary.

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Check understanding

Classifies given changes as physical or chemical with justification
Explains what conservation of mass means and why mass is conserved in chemical reactions
Names observable signs that a chemical reaction has occurred (colour change, gas produced, temperature change, precipitate)
Explains why dissolving is a physical change but burning is a chemical change

“If your child dissolved sugar in tea versus burnt toast in the toaster, could they explain which is a physical change and which is a chemical change — and what test would show that mass is conserved in both cases?”

Curriculum record

Type: Conceptual
Subject: Science
Domain: Matter & Materials
Age range: Ages 11–13

Standards

ngss-ms:MS-PS1-2ngss-ms:MS-PS1-5uk-nc-2013:KS3.Sci.Chem.AEC.4uk-nc-2013:KS3.Sci.Chem.PIS.5