Teach lesson
Choosing a material: hardness, toughness, and strength
Students use the Materials remote lab to compare hardness, impact, and tensile evidence and recommend a material combination for a part that may be scratched, struck, or subjected to loading that could cause yielding or failure.
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Learning Outcomes
Distinguish hardness, toughness, and strength as different properties.
Assess the preliminary suitability of a material / alloy / treatment combination using lab-session and reference evidence.
Relate a laboratory test to a design need.
Avoid conclusions such as 'the hardest material is always the best'.
Defend a material choice with evidence and a limitation.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
1. The design problem
8 min
Imagine that you must choose a material for a small part used in a school workshop. Tools may scrape it, it may be struck, and it must withstand its working load without permanently deforming or breaking.
There is no single property that makes something “a good material.” In this activity, you will compare three different properties:
- Hardness: resistance to marks or scratches on the surface.
- Toughness: the ability to absorb an impact without brittle fracture.
- Mechanical strength: the ability to withstand tensile stress or loading before yielding (permanent deformation) or breaking. This differs from stiffness: stiffness and the part's geometry affect how much it bends elastically under load.
Illustrative reference: Materials introduction
This illustrative reference screenshot shows the navigation and entry point for the pre-recorded lab experience. It does not confirm which material cards, categories, test methods, or routes are available in the current session.
Before opening the lab, state which property you think is most important for the workshop part: hardness, toughness, or mechanical strength. Justify your choice with a specific situation.
2. Observe material tests
22 min
The lab lets you select a material, alloy, treatment, and test method. Use only the verified route or another route that is visibly available in your session, separately verified by your teacher before class, and then assigned. If the screen shows a number, copy the unit as well. If it only shows an image or video, describe the visible evidence.
Illustrative reference: material and alloy selection
This illustrative reference screenshot shows how material cards and alloy categories may be arranged. The displayed cards, categories, and options do not confirm what is available in the current session. The cards' general descriptions are not comparable evidence tied to a specific alloy and treatment; do not use them to justify the recommendation.
Illustrative reference: older test selection
This illustrative reference screenshot from an older interface shows a Steel / 14301 / As delivered / Tensile test configuration. It helps identify the parts of the interface, but it does not establish current route availability and must not be used as a selection instruction. Its simplified hardness wording should not be read as a definition of strength: in this lesson, hardness means resistance to local surface indentation, marking, or scratching, while strength concerns loading or stress before overall yielding or failure.
Open Materials and gather evidence
Open the Materials lab from this activity.
Run the verified route, selecting these exact interface labels: steel → 1.4301 → as delivered → Hardness measure → HV1. Here,
HV1identifies the Vickers test condition shown by the interface; it is not, by itself, the unit of a hardness result.Run another route only if it is visibly available in your session, your teacher has separately verified the complete route before class, and your teacher assigns it. If a method is available, select its exact interface label, such as Notched bar impact test or Tensile test; do not assume that a particular material, alloy, or treatment route will be available.
For each route you run during the session, record the material, alloy, treatment, method, and observed evidence. Mark the source as Lab-session evidence.
Your teacher will provide clearly labelled Teacher-provided reference evidence for any required property that you cannot observe during the session. Copy its material / alloy / treatment combination and keep that label in your table.
45-minute option: run the verified hardness route and use two concise teacher-provided reference rows, one for impact and one for tensile behaviour.
55-minute option: run the verified hardness route and any additional route that is visibly available, separately verified by your teacher, and assigned. Add fuller notes about the evidence and its limitations. Use teacher-provided reference rows for inaccessible or unverified routes.
Keep the properties separate: a hardness test supports a conclusion about hardness, not toughness.
Evidence of material properties
Complete at least three rows: the verified hardness route from the session plus impact and tensile evidence. Label every row 'Lab-session evidence' or 'Teacher-provided reference evidence', and record the exact session, source title, or source identifier in 'Exact evidence source'. In the 45-minute option, enter one concise evidence note per row while still completing every required cell. In the 55-minute option, record any additional route that was visibly available, separately verified by your teacher, assigned, and actually run during the session; give fuller evidence and limitation notes. Under 'Confidence and reason', write High, Medium, or Low and explain why.
| Test and evidence source | Exact evidence source | Material / alloy / treatment | Property tested | Observed evidence | Number and unit, if shown | Confidence and reason |
|---|---|---|---|---|---|---|
Which statement makes the best use of the laboratory tests?
3. Make a criteria-based decision
15 min
Illustrative reference: older tensile observation area
This illustrative reference screenshot from an older interface shows the Steel / 14301 / As delivered / Tensile test configuration, video and controls, and the literal Tensile test plot heading; no plot is visible. It does not establish that a plot, CSV, or numerical export is available, does not confirm current route availability, and is not a selection instruction. A value and unit that are actually visible may still be recorded as observation evidence. State which kind of evidence you actually used.
Choose two properties that represent potentially competing design requirements for the workshop part. Explain why both matter, then assess whether your table contains comparable evidence for the same material / alloy / treatment combination. Do not claim or imply a trade-off or opposing relationship unless both properties were measured comparably for at least two candidate combinations or conditions and show that opposing pattern; otherwise, state what comparison is still needed.
For the workshop part, name the best-supported preliminary material / alloy / treatment candidate, or state explicitly that the available evidence is inconclusive. Use test evidence and identify the exact evidence from the same material / alloy / treatment combination, acceptance threshold, or valid comparison still needed before making a firm decision.
4. Final recommendation
10 min
Write a preliminary recommendation for the workshop manager. Include:
1. The best-supported material / alloy / treatment candidate, or an explicit statement that the recommendation is inconclusive if no candidate is adequately supported.
2. Two pieces of test evidence, which may combine the verified session route with clearly labelled teacher-provided reference evidence. State whether each item applies directly to the named combination or is only a comparison.
3. One property for which the evidence supports preliminary suitability, and why that property matters for the part's intended use. If no threshold or matched comparison supports “performs well,” say that performance is not yet established.
4. The exact missing evidence for the same material / alloy / treatment combination and property, acceptance threshold, or valid comparison needed before making a final decision.
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