Evidence of Chemical Change

Overview

In this final lesson of the three-part unit “Elements, Compounds, and Change,” students use visual evidence to distinguish physical from chemical changes. A teacher-led investigation builds on prior learning about states, mixtures, elements, and compounds while connecting materials such as plastic, rubber, and clay to natural resources, synthetic materials, and effects on society.

Learning intentions

Students will be able to:

• Identify evidence that a new substance may have formed.
• Distinguish physical changes from possible chemical changes.
• Recognize gas production, color change, precipitate formation, and thermal-energy change.
• Connect changes in materials to natural resources, synthetic products, and society.

Success criteria

• I can sort an example as a physical change or possible chemical change.
• I can identify evidence such as gas, color change, a precipitate, or a temperature change.
• I can explain that evidence of a chemical change suggests a new substance formed.
• I can describe one way a material change affects people or the environment.

Curriculum links

• Matter and changes: identify formation of a new substance using evidence of a possible chemical change.
• Matter and changes: compare solids, liquids, and gases by structure, shape, volume, and particle kinetic energy.
• Matter and changes: investigate physical properties and distinguish pure substances and mixtures.
• Science practice: observe, classify, use evidence, and communicate an explanation.

Lesson structure (30 minutes)

1. 0–4 min · Visual hook. Teacher opens with the hook and mystery-change images showing an ice cube melting, paper burning, and a tablet fizzing in water, then asks, “How could we tell whether a new substance formed?” Students silently choose a physical-change or chemical-change signal and share one observation with a partner.

2. 4–9 min · Teach the evidence. Teacher uses the evidence-of-change slides to introduce the four clues: gas production, color change, precipitate formation, and thermal-energy change; emphasize that one clue is evidence of a possible chemical change, not automatic proof. Students sketch or match each clue to a simple visual and repeat the sentence frame: “I observe ___, so a new substance may have formed.”

3. 9–18 min · Teacher-led investigation. Teacher demonstrates four safe, highly visual examples, pausing after each: an ice cube melting (physical change), baking soda and vinegar in a sealed balloon or bag (gas), two clear solutions mixed to form a cloudy solid (precipitate), and an instant cold pack or sealed temperature-change demonstration (thermal energy); use the investigation observation slides for the numbered examples and safety reminders. Students record what they see, hear, or feel on the chemical-change evidence recording sheet and hold up a “physical” or “possible chemical” response for each example.

4. 18–24 min · Sort and justify. Teacher displays picture scenarios on the sorting activity slides, including cutting clay, stretching rubber, melting plastic, rusting metal, burning fuel, and mixing materials. In groups of three or four, students sort the scenarios on their worksheet and justify two decisions using “My evidence is ___.” Teacher probes: “Did the shape change only?” and “What evidence suggests a new substance?”

5. 24–27 min · Materials and society connection. Teacher briefly explains that clay and rubber can come from natural resources, while many plastics are synthetic materials made through human processes; show the natural-and-synthetic-materials discussion slide. Students choose one material and state one useful effect and one possible concern, such as durability, waste, pollution, or conserving resources.

6. 27–30 min · Exit check. Teacher displays the review and exit-ticket prompt and asks students to complete the final section of the chemical-change evidence recording sheet: “A clear liquid becomes cloudy after mixing. What evidence is present, and why might a new substance have formed?” Students submit the worksheet as they leave.

Resources

• Teacher computer and projector
• the complete Evidence of Chemical Change slide deck
• the chemical-change evidence recording sheet
• Ice cube and shallow tray
• Baking soda, vinegar, sealable bag or balloon, and tray
• Two safe clear solutions that form a visible precipitate when mixed
• Instant cold pack or teacher temperature-change demonstration
• Safety goggles, paper towels, and waste container

Assessment

• During the investigation, check whether students correctly identify the observed clue and distinguish melting from a possible chemical change.
• Listen for evidence-based explanations during sorting; prompt students to name an observation rather than simply say “chemical.”
• Use the exit response to assess whether students can identify a precipitate and connect it to possible formation of a new substance.

Differentiation

• Provide picture icons and the sentence frames “I observe ___” and “This may be chemical because ___.” Allow students to point, draw, or verbally respond instead of writing every observation.
• Pair students strategically and assign roles such as observer, recorder, materials monitor, and reporter; read worksheet directions aloud and use large, high-contrast visuals for EAL and SEN learners.
• For students needing additional support, limit the first sort to melting, cutting, fizzing, and color-change examples before adding the full set.
• Challenge early finishers to explain why a change in shape or state does not necessarily create a new substance and to identify what additional evidence they would collect.