Chemical Modelling

Overview

Today students model and represent different substances using particles/atoms and scientific thinking, then link these representations to the idea of chemical reactions as “evidence of new substances”. The lesson builds directly from atoms, elements, and compounds to modelling particle arrangements and starting to describe reactions using word equations.

Learning intentions

• WALT represent substances (atoms, elements, compounds) using scientific models and particle diagrams.
• WALT use observable evidence to explain that a chemical reaction forms new substances.
• WALT describe simple chemical reactions using word equations.
• WALT justify a model/representation using particles and bonding ideas.

Success criteria

• I can draw a particle model for an element and for a compound that shows different atoms bonded together.
• I can explain what my model shows using correct science vocabulary (atom, element, compound, chemical bond).
• I can identify evidence that a chemical reaction has occurred (e.g., new substance formed, gas produced, colour change, temperature change).
• I can write a simple word equation for a basic reaction using correct reactants and products.

Curriculum links

• Science (Nature of Science): Students use evidence and modelling to develop and communicate explanations about chemical changes.
• Science (Chemical reactions): Students observe chemical reactions and provide evidence that a chemical reaction has taken place.
• Science (Matter): Students build from “all matter is composed of atoms” to representing atoms and substances as particle models.
• Science (Chemical reactions): Students use word equations to describe basic chemical reactions.
• Thinking and using language (NZC Refresh competencies): Students communicate scientific ideas clearly, using appropriate terms and models, and use evidence to reason.

Lesson structure (90 minutes)

1. 0–10 min · Retrieval and focus. Teacher runs a quick “Model or No?” quiz on the board (e.g., single-atom picture, two different atoms bonded, mixed dots with no bonds). Students write a one-sentence justification for each choice in pairs.
2. 10–25 min · Mini-lesson: modelling substances. Teacher explicitly teaches a consistent modelling rule-set: atoms as circles labelled by element, elements as identical atoms, compounds as different atoms chemically bonded (show bonds as lines). Students revise their model vocabulary and annotate a sample diagram.
3. 25–45 min · Research task: build a “Substance Profile”. Students work in groups of 3–4. Each group draws and labels particle models for 3 given substances (teacher provides cards with descriptions such as “a substance made of one type of atom” and “a substance made of two different atoms bonded”). They must also add 2 evidence statements: “What would you observe if it were a pure substance?” vs “What would you observe if it were a mixture?” (kept brief because mixtures come next week). Teacher circulates with prompts: “How do you know it’s a compound in your model?” and “Where are the bonds?”
4. 45–55 min · Gallery walk and feedback. Groups post one model and explanation. Students use a checklist to give feedback: accurate labels, bonding shown correctly for compounds, and clear explanation of what particles represent.
5. 55–70 min · Introducing chemical reactions with safe evidence. Teacher demonstrates or shows a short simulation (no hazardous materials): options such as fizzing (bicarbonate + acid), colour change (indicator reaction), or temperature change setup. Students record observations in a table under “Before / During / After”. Teacher prompts: “What new substance is being formed?” and “What is the evidence?”
6. 70–80 min · Word equations for beginners. Teacher introduces a simple structure for word equations: reactants → products. Students, in pairs, convert the demonstration into a word equation using sentence stems (e.g., “reactants are ___ and ___; products are ___”). Teacher checks for correct naming rather than balancing coefficients (not the focus today).
7. 80–90 min · Creative task + exit evidence. Students choose one:

• Atom construct: build an atom using materials (paper circles/beads) and then draw a particle model showing how it would appear in an element or compound.
• Creative drawing: create a “Substance Scene” poster showing particles for an element and a compound, plus one small “reaction evidence” panel (e.g., “new colour appears”). At the end, students complete an exit ticket: one sentence identifying evidence of a chemical reaction and one word equation from the demo.

Resources

• Substance description cards (elements/compounds) and blank particle-diagram templates
• Label stickers or pens for element symbols (e.g., A/B placeholders if not using chemical formulas yet)
• Group observation table (Before/During/After)
• Simple demo materials or prepared simulation/video (teacher-selected safe option)
• Word equation sentence stems
• Creative task materials (beads/pipe cleaners/paper circles, glue, markers)
• Feedback checklist for gallery walk
• Exit ticket slips

Assessment

• Formative during modelling: teacher checks group diagrams for correct “element = identical atoms” and “compound = different atoms bonded”.
• Formative feedback during gallery walk: students use checklist to confirm and improve explanations.
• Exit ticket: evaluates evidence-based reasoning about chemical reactions and ability to produce a basic word equation.

Differentiation

• Support: provide partially completed particle diagrams and word-equation sentence starters; allow students to use A/B naming instead of unfamiliar element symbols.
• Support for reasoning: sentence frames for “My model shows ___ because ___.”
• Extension: ask students to propose an additional observable evidence that could confirm a reaction in a different context (e.g., “If it produced a gas, what would we see?”).
• EAL/SEN: allow vocabulary cards, reduced writing load (one key sentence), and structured group roles (diagramner, label-checker, evidence writer).