Metal Alloys Simulation — Description
The simulation shows a 3D hexagonal close-packed metallic lattice (6 rows × 9 columns × 3 deep) that students can orbit, zoom, and interrogate by hovering individual atoms. Three controls drive the core chemistry:
⚗ Alloy transitions the lattice from pure metal to alloy — substitutional atoms grow in at pre-seeded lattice sites (brass, bronze) or interstitial carbon atoms emerge from the gaps between iron rows (steel). The size and colour change is animated so students can watch the distortion develop.
↔ Force applies a shear across the lattice midpoint. In pure metal the top half slides freely with large, visible displacement. In alloy mode the movement drops dramatically — the different-sized atoms jam the layers. A translucent slip plane turns cyan when sliding freely and red-orange when blocked.
⚙ Steel / 🔶 Brass / 🟤 Bronze switches alloy type with a clean reset. Each has accurate relative atom sizes: carbon is much smaller than iron (interstitial, ~61% radius), zinc is slightly smaller than copper (substitutional, ~95%), tin is larger than copper (substitutional, ~109%). Real atomic radii are cited in the hover tooltips.
The Labels / Teach panel surfaces five contextual AQA states — pure lattice, pure metal sliding, distorted lattice, blocked alloy, and overview — updating automatically as students interact. Hover tooltips distinguish base metal ions, substitutional sites, and interstitial atoms with exam-accurate language.
Suggested Class Activity
“Why Is Steel Stronger Than Iron?” — Guided Enquiry (30–40 min)
This works well as a paired or small-group station activity, or as a whole-class live demo on a projector (press C to switch to classroom display mode).
Stage 1 — Predict (5 min)
Before opening the simulation, show students these two questions on the board:
Pure iron is soft enough to bend. Steel holds up bridges. They’re both mostly iron. What must be different? What would you need to add to a regular arrangement of identical balls to stop them sliding?
Students write a prediction in their books. No right answer expected — the point is to activate prior thinking about structure and properties.
Stage 2 — Explore: Pure Metal (8 min)
Students open the simulation with no buttons pressed.
Task card:
- Drag to orbit the lattice. What pattern do you notice about how the atoms are arranged?
- Press ↔ Force. What happens to the top half of the lattice?
- Press Force off. What does this tell you about why pure metals are malleable and ductile?
- Hover over any atom. What does the tooltip tell you about metallic bonding?
Students record observations. Key vocab to elicit: regular lattice, identical atoms, delocalised electrons, layers slide, malleable, ductile.
Stage 3 — Explore: Steel (8 min)
Press ⚙ Steel (alloy activates automatically).
Task card:
- What has appeared in the gaps between iron atoms? Hover on the dark atoms — read the tooltip.
- Now press ↔ Force. What is different compared to pure iron?
- Look at the slip plane colour. What does red mean?
- Press 🏷 Labels for the AQA explanation. Write the key sentence in your own words.
Key question to discuss: Why can’t the carbon atoms replace the iron atoms? (size — too small.)
Stage 4 — Compare: Brass and Bronze (8 min)
Students switch to 🔶 Brass and 🟤 Bronze in turn, applying force each time.
Comparison table (students complete):
| Steel | Brass | Bronze | |
|---|---|---|---|
| Base metal | |||
| Added element | |||
| Type of alloy | |||
| Added atom: bigger or smaller? | |||
| Does force block sliding? |
Key discussion: Brass and bronze are both substitutional — what is the difference between them and steel? Leads naturally to AQA’s interstitial vs substitutional distinction.
Stage 5 — Consolidate (5 min)
Exit ticket — students answer without the simulation open:
Explain, using ideas about structure and bonding, why steel is harder than pure iron. Use the words: lattice, interstitial, layer, sliding, distort. (4 marks, AQA style)
Adaptation notes
For students who need additional support, keep 🏷 Labels on throughout and direct attention to the teach panel sub-text before asking them to write. The Accessibility modal offers Irlen overlays, dyslexia spacing, reading ruler, and extra-slow motion — useful for the Force animation in particular. The three-tier assessment in ClassAdapt (Supported / Guided / Independent) maps directly onto the five stages above.