A bridge cable, a saucepan, a drink bottle and a phone screen are all chosen for reasons. In Stage 5 science, materials are not just named or described. They are assessed using evidence about their physical and chemical properties, and that is the foundation for this whole unit.
Use the PDF for classwork, homework or revision. It includes key ideas, activities, questions, an extend task and success-criteria proof.
Many students answer these questions with one-word ideas like "strong" or "cheap". Science needs a better standard. Before learning the formal language, write what properties you think make one material suitable and another unsuitable.
Think about the screen, the frame and the buttons. Each part does a different job. What does that tell you about how engineers choose materials?
A useful material is not simply "good". It is good for a specific purpose because its properties match the demands of that purpose.
Think about a bridge cable, a frying pan, an electrical wire and a takeaway cup. These objects do not need the same properties. A bridge cable needs high strength. A frying pan needs to tolerate heat. A wire must conduct electricity well. A takeaway cup should be light and practical for short-term use. This is why science studies materials through evidence rather than preference.
In this unit, students will keep returning to the same core question: which material is most suitable, and how can that judgement be justified using science? That shift from naming to assessing is the key Stage 5 move.
Students often focus on the most obvious physical features, such as hardness or flexibility, and ignore chemical behaviour. That is too narrow. Many materials are chosen or rejected because of both how they physically behave and how they react chemically.
A saucepan is not only useful because it is strong. It also needs a high melting point and should not react dangerously during normal cooking use. A structural metal is not only judged by strength. It may also be judged by how quickly it corrodes in air or salt water. This is why both physical and chemical properties matter.
Real material choice is rarely perfect. One material might be strong but heavy. Another might be cheap but chemically unstable. Another might be durable but difficult to recycle. Assessing materials means making a justified judgement based on the criteria that matter most in a specific situation.
Consider the decision process an engineer uses. First, they ask what the object needs to do. Then they gather evidence about which properties matter. Finally, they compare options against clear criteria. The result is not always one perfect material. It is the best balance of properties for that specific use.
A material can perform its job perfectly and still be a poor choice if it creates serious environmental harm. Stage 5 science asks students to extend their assessment beyond performance to include environmental impact across the full lifecycle of a material.
Scientists and engineers now consider not just whether a material works, but how it is extracted, how long it lasts, how it is disposed of, and what happens to it after use. This full-lifecycle thinking is why materials like biodegradable packaging and recycled aluminium are increasingly preferred over materials that perform identically but persist in the environment for centuries.
In this unit, the environmental dimension appears throughout — from finite mineral resources to hydrocarbon combustion to polymer waste. Every material assessment decision in Stage 5 Science should consider both performance and impact.
Wrong: "All useful materials are chosen only by physical properties."
Right: Chemical properties matter too. Corrosion, flammability and reactivity all determine whether a material is safe and suitable for its purpose.
Wrong: "Organic means natural and inorganic means man-made."
Right: In science, organic means carbon-based. Both natural and synthetic materials can be organic or inorganic. Petroleum is natural and inorganic; synthetic polymers are man-made and organic.
Right: Chemical properties determine safety and suitability. A material that corrodes quickly or burns easily is unsuitable even if it looks strong.
Right: Cost is only one criterion. Strength, safety, durability, weight and environmental impact also matter. The best choice balances all relevant criteria for the specific use.
Drag each property into the correct category: Physical or Chemical.
Materials are chosen because their physical and chemical properties suit a particular purpose.
Physical properties can be observed or measured without turning the substance into a different substance.
Chemical properties describe how a substance behaves in a chemical change, such as reacting, burning or corroding.
To assess a material means to make a judgement using evidence and clear criteria, not just to describe it.
Choose three everyday objects and explain which properties matter most for each one. You do not need the exact perfect answer yet. Focus on the reasoning.
A student wrote: "Steel is the best material because it is strong." Explain why this answer is incomplete and rewrite it using scientific criteria.
Claim: State whether the answer is strong or weak and why.
Evidence: Use facts from the lesson about what good material assessment requires.
Reasoning: Explain how the evidence shows the answer is incomplete, then rewrite it.
1. What does it mean to assess a material?
Which option does not describe what it means to assess a material?
2. Which is a physical property?
3. Why can chemical properties matter in material selection?
4. Which property would most directly matter when choosing a material for electrical wiring?
5. Which statement best reflects the big idea of this lesson?
Explain the difference between a physical property and a chemical property. 1 mark for defining physical property. 1 mark for defining chemical property. 1 mark for a valid example of each.
A class is choosing between glass and plastic for a drink bottle. Explain two criteria they should consider and why. 1 mark for each criterion identified (2). 1 mark for each criterion linked to a relevant property (2).
Why is saying "metal is best" poor scientific reasoning when discussing materials? 1 mark for identifying that "best" requires criteria. 1 mark for explaining that different uses need different properties. 1 mark for linking to physical properties. 1 mark for linking to chemical properties. 1 mark for proposing a stronger, evidence-based statement.
Return to the opening questions. Can you now explain the material choices using clearer scientific criteria rather than everyday guesswork?
1: C. Assessing means making a judgement using evidence and criteria. Naming or guessing is not assessment.
2: A. Density is a physical property because it can be measured without changing the substance. Flammability, corrosion and reactivity all involve chemical change.
3: D. Chemical properties matter because reacting, burning or corroding can make a material unsafe or unsuitable for its purpose.
4: B. Electrical conductivity directly matters for wiring because the material must allow electric charge to flow. Transparency and biodegradability are irrelevant, and a low boiling point would be dangerous.
5: C. Materials are assessed by matching their properties to the demands of a purpose. No single material is best for everything.
Sample answer: A physical property can be observed or measured without changing the substance into a different substance. A chemical property describes how the substance behaves in a chemical change. For example, density is a physical property and flammability is a chemical property.
1 mark for defining physical property. 1 mark for defining chemical property. 1 mark for a valid example of each.
Sample answer: One criterion is mass or weight, because a lighter bottle (plastic) may be easier to carry than a heavier one (glass). Another criterion is toughness or shatter resistance, because a bottle that breaks easily (glass) may be unsafe if dropped, whereas plastic is less likely to shatter. These criteria help assess which material is more suitable for the intended use.
1 mark for each criterion identified (2). 1 mark for each criterion linked to a relevant property (2).
Sample answer: The statement is poor because "best" is meaningless without clear criteria and a specific use. Different uses need different properties: a bridge needs high strength, but a phone needs low mass. Physical properties such as density and conductivity matter, and chemical properties such as corrosion resistance also affect suitability. A stronger statement would be: "Steel is a suitable material for bridge cables because it has high tensile strength and good durability, though it may corrode in salt water unless protected." This uses evidence and criteria rather than a vague claim.
1 mark for identifying that "best" requires criteria. 1 mark for explaining that different uses need different properties. 1 mark for linking to physical properties. 1 mark for linking to chemical properties. 1 mark for proposing a stronger, evidence-based statement.
Materials are chosen because their properties suit particular jobs.
Physical and chemical properties both matter when evaluating suitability.
Stage 5 science expects judgements based on evidence and criteria.
Next lesson deepens this by looking more closely at physical properties and how they guide material selection.
Jump through questions on physical vs chemical properties and what makes materials useful. How high can you go?