Hard to Classify Matter

Overview

Today students explore matter that is hard to classify using the particle model, then connect ideas about state changes to real-world problem solving. This lesson builds on earlier work classifying substances as solids, liquids and gases, and using particle motion to explain observable properties.

Learning intentions

• Students will investigate how some substances don’t fit neatly into solids, liquids or gases.
• Students will model particle arrangement and motion to explain observable properties of unusual matter (e.g. plasma, non-Newtonian fluids).
• Students will plan and run a short, safe, repeatable investigation to collect evidence about a chosen “hard to classify” material.
• Students will use results and a comparison with another group’s findings to draw a reasoned conclusion about what is happening when a material changes state or behaves unusually.

Success criteria

• I can classify the observable behaviour of an unusual matter sample and justify it using the particle model.
• I can describe how particles are arranged and moving in my explanation.
• I can collect repeatable observations and present them in a simple table.
• I can compare findings with another group, identify errors or sources of variation, and state what I would test next.

Curriculum links

• Science — explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• Science — plan and conduct repeatable investigations, including deciding variables, measuring and controlling a fair test, identifying risks and using equipment safely.
• Science — compare methods and findings with those of others, recognise possible sources of error, and draw reasoned conclusions using evidence.
• Science — investigate how scientific knowledge helps communities make decisions and solve problems.

Lesson structure (80 minutes)

1. 0–8 min · Hook: “Still matter?” Teacher shows 3 short images/video clips: plasma-like glow, a non-Newtonian fluid demonstration (e.g. oobleck behaving solid-like when struck), and a freeze-drying/cooking process photo. Students record quick “What state is it?” guesses and one observable clue for each.

2. 8–20 min · Direct teach: particle model for unusual cases Teacher revises: solids keep shape/volume, liquids keep volume, gases fill space; then explains that some substances show behaviours that don’t match neatly because particle behaviour can change with conditions (e.g. temperature, pressure, mixing, or force). Students use a simple particle diagram template (solid/liquid/gas) and add “an extra label” for how their unusual sample might require a modified explanation (e.g. “particles don’t behave like a normal liquid under force”).

3. 20–35 min · Safety and investigation planning Teacher introduces today’s group task: choose ONE material station (non-Newtonian fluid demonstration set OR “state change” application activity card) and plan a short fair test to gather evidence. Students complete a quick method plan:

• Variable to change (e.g. force applied: gentle press vs fast strike; or time/temperature for a state-change step)
• What to measure (e.g. how far a probe sinks, time to reach a visible change, or number of repeated trials showing the same behaviour)
• What to control (same container, same volume/mass, same tool, same trial count)

4. 35–55 min · Investigation (repeatable evidence) Teacher supervises and monitors safety: eye protection where needed, wipe/spill procedures, and controlled pouring. Students conduct 3 trials, record observations immediately in a table (condition → observation → evidence). If they choose non-Newtonian fluid, they test “force changes behaviour” with the same amount and tool; if they choose a state-change application card, they follow the prescribed procedure using safe materials and observe measurable changes.

5. 55–65 min · Compare with another group Teacher pairs groups to exchange results and methods. Students answer: “Was it a fair test?” “Did we change the same variable?” “What evidence do we both agree on?” They note one possible source of error (e.g. different force, inconsistent timing, measurement misread, different container shape).

6. 65–75 min · Real-world application mini-discussion Teacher prompts: “Where would understanding state change help solve a problem?” Options: freeze-drying for food/medicine stability, cooking (evaporation/condensation), industrial processes (heating/cooling). Students complete a “Problem → Science idea → Decision” sentence stem.

7. 75–80 min · Exit ticket Students respond:

• “My sample behaved like…” (solid/liquid/gas/other)
• “Using particles, it makes sense because…”
• “One improvement for next time is…”

Resources

• Particle model diagram sheets (solid, liquid, gas + blank “unusual” section)
• Unusual matter station set (e.g. oobleck/non-Newtonian fluid demo materials, trays, tools for consistent poking/pressing, paper towels)
• “State change applications” picture cards (freeze-drying, cooking/boiling/condensation, industrial heating/cooling)
• Safety equipment (glasses where appropriate, gloves if using messy materials)
• Measuring tools (measuring cups/spoons, ruler, timer)
• Data tables (condition, trial, observation, evidence note)
• Wipeable board + markers, student notebooks
• Bin liners and wipes for quick cleanup
• Teacher risk plan reminder (spills, food safety, hygiene)

Assessment

• Observation during investigation: correct variable identification, safe equipment use, accurate trial recording.
• Check-ins during partner comparison: students explain whether it was a fair test and cite evidence from their table.
• Exit ticket: identifies classification/behaviour and uses a particle-based justification; includes one valid improvement.

Differentiation

• Support: provide sentence starters for planning (“We will change…”, “We will measure…”, “We will keep…”) and a partially completed method table for students who need structure.
• Support: offer a “particle prompt card” (arrangement/motion words) so students can translate their observations into particle explanations.
• Extension challenge (advanced learners): add a second variable (e.g. temperature of the non-Newtonian fluid or different container shapes) and propose a new fair-test question, including what evidence would best support their claim.
• For EAL/SEN: allow oral recording or diagrams in addition to written notes; pre-teach key terms like “state change”, “particles”, “motion”, “arrangement”, “evidence”, “repeatable”.

Extension (optional)

• Advanced inquiry: research plasma in technology (e.g. plasma screens, sterilisation, welding) and prepare a short “How does particle behaviour help solve a problem?” explanation, using one piece of evidence from the investigation or from trusted classroom resources.
• Design challenge: if oobleck is used, design a follow-up experiment that tests how changing concentration affects its behaviour, ensuring only one variable changes at a time.