Introduce physical properties: the things we can observe or measure about a material without changing what it is. Build a class word wall of property words — hard, strong, flexible, transparent, absorbent, waterproof, brittle — illustrating each with a classroom object ("the window is transparent; the sponge is absorbent").
Model fit-for-purpose reasoning with a think-aloud: "A hammer needs to be hard and strong. Could we make a hammer out of glass? Glass is hard, but it is brittle — it would shatter. So glass is the wrong material for a hammer." Show a labelled diagram of one object (e.g. a drink bottle) naming its material and properties.
Play the guess-the-material feely-bag game: a student reaches in, and instead of naming the object, names the material and a property they can feel. Then, in pairs, students examine a set of familiar objects with magnifying glasses and discuss, for each: its use, the properties it needs, the material it is made from, and why that material fits.
Pose "what if" swaps to the class — "What if shirts were made of glass? What if a window were made of wood?" — drawing out property-based reasoning each time.
Students complete the Material Detectives worksheet: matching properties to meanings, examining three classroom objects (material + property + why it suits the job), deciding which properties make glass good for a window, and explaining what would happen if a drink bottle were made of paper.
Exit ticket collected: the paper-bottle explanation with a property-based reason.