Materials: Properties, Uses & Impacts — Practice · Grade 8 Science

Chapter: Properties of Matter

What this practice covers

By the end of Materials: Properties, Uses & Impacts you should be able to:

11 questions, multiple choice and written answer, each with a worked explanation.

Vocabulary used: synthetic material, constraint, trade-off, model, evidence, system boundary, assumption.

Problem 1

Which property matters most for an electrical wire’s inner material?
  1. Color
  2. Electrical conductivity
  3. Odor
  4. Transparency
Answer and explanation

Electrical conductivity

Charge must move through the wire.

Problem 2

Why is “synthetic means unsafe” not a sound conclusion?
Answer and explanation

Safety depends on the specific material, exposure, and use, not only its origin.

Problem 3

Give one benefit and one drawback of a durable plastic container.
Answer and explanation

It can be reused because it is durable; its durability can also make discarded waste persist.

Problem 4

Bag A survives 2 trips and uses 20 g of material; bag B survives 20 trips and uses 100 g. Compare material per trip, ignoring other impacts. Explain the reasoning in your own words.
Answer and explanation

B uses 5 g/trip versus A's 10 g/trip in this model; the model alone does not settle total environmental impact.

Divide each bag's material by its number of trips: 20/2 and 100/20.

Compare 10 g/trip with 5 g/trip, while noting that energy, cleaning and disposal are not included.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

A lunch box uses 240 g of material and lasts 120 uses. Find material per use and state one limitation. Show the reasoning, not just the conclusion.
Hints

Equivalent trips must be compared; weight of one unused bag is insufficient.

Answer and explanation

240/120=2 g/use. This omits production energy, cleaning and disposal and assumes all 120 uses occur.

Problem 6

Material X is strong but corrodes in salt water; Y is slightly weaker but corrosion-resistant. What evidence should decide a seaside design?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Compare required load capacity and durability under salt exposure, then cost and other constraints. Strength alone cannot decide suitability.

Problem 7

Which stage is measured by a one-minute leak test?
Answer and explanation

One use-performance feature. It does not measure extraction, manufacturing energy, lifetime reuse or disposal impacts.

One use-performance feature. It does not measure extraction, manufacturing energy, lifetime reuse or disposal impacts.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 8

Illustrative container trials give material A 0 leaks in 3 tests but only 2 successful reuse cycles; B 1 leak in 3 tests and 20 reuse cycles. Costs and manufacturing impacts are unknown. Choose a provisional material for one stated use. Compare water resistance and reuse, and specify a missing measurement instead of declaring a universal winner.
Answer and explanation

For a leak-sensitive one-time model test, A’s observed leak record is favorable. For repeated use, B’s larger tested lifetime matters, but one observed leak requires improvement or further testing. Cost and full environmental impacts remain unknown. A recommendation must identify the intended criterion and hard constraints rather than combine unlike measures without a rule.

For a leak-sensitive one-time model test, A’s observed leak record is favorable. For repeated use, B’s larger tested lifetime matters, but one observed leak requires improvement or further testing. Cost and full environmental impacts remain unknown. A recommendation must identify the intended criterion and hard constraints rather than combine unlike measures without a rule.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 9

Use the supplied two source records to explain one benefit, one concern and a needed follow-up for a film/container choice. Do not treat a resource label as a full safety or impact rating.
Hints

Use the illustrated study titled Natural resources and different plastics. Keep the observations, model and conditions separate.

Answer and explanation

The reuse record supports longer tested service for the rigid container, while the disposal record warns that acceptance depends on product and local processing. Resource origin alone does not establish total impacts. Compare the same task, include cleaning and replacement, and obtain specific production/disposal information. Describe chains and processing as a plausible property explanation rather than proof from the label plastic.

The reuse record supports longer tested service for the rigid container, while the disposal record warns that acceptance depends on product and local processing. Resource origin alone does not establish total impacts. Compare the same task, include cleaning and replacement, and obtain specific production/disposal information. Describe chains and processing as a plausible property explanation rather than proof from the label plastic.

Response criteria

  • Connect a synthetic material to a resource and processing.
  • Use two different source records.
  • Assess benefits, concerns and missing evidence fairly.

Problem 10

Material arrangement affects how energy crosses a containerMaterial arrangement affects how energy crosses a containerSingle wallTwo walls + air gapA gap can reduce one conduction pathway; it does not stop all transfers.Structure changes a mechanism. Test the resulting temperature and other criteria.
The two schematics distinguish a single wall from an arrangement with two walls and an air gap. A gap can reduce some conduction pathways, while radiation, air movement and contact bridges can still transfer energy. The model predicts a mechanism, not a guaranteed performance ranking without comparable measurements. Wall thickness, sealing, material amount and cost also matter.
For this unit’s illustrated case, why is “two walls means no heat can enter” not supported? Name a remaining pathway and a relevant test.
Answer and explanation

Radiation or conduction through contacts can remain, and moving air may contribute. Compare matched temperature-versus-time records and other design criteria instead of claiming all energy transfer stops.

Structure describes how materials are arranged; a property describes their measured response under conditions. Processing and assembly can change the arrangement. A useful design explanation connects the feature to a particular mechanism and a measurable outcome.

Radiation or conduction through contacts can remain, and moving air may contribute. Compare matched temperature-versus-time records and other design criteria instead of claiming all energy transfer stops.

Response criteria

  • Use the named labels, directions or supplied quantities accurately.
  • Connect the visual evidence to the scientific mechanism or calculation.
  • State the relevant model conditions or limitation.

Problem 11

Cup A can be used 20 times and needs 8 material-units per cup; B is single-use and needs 2 units each time. Compare raw material for 20 uses, then name two omitted impacts before declaring an environmental winner.
Answer and explanation

A uses 8 initial material-units; B uses 40 for 20 cups. Cleaning energy/water, production, transport, disposal and actual lifetime are omitted, so initial material alone is not a complete impact ranking.

Compare the same amount of service.

Keep the measured raw-material comparison separate from the full life cycle.

A uses 8 initial material-units; B uses 40 for 20 cups. Cleaning energy/water, production, transport, disposal and actual lifetime are omitted, so initial material alone is not a complete impact ranking.

Response criteria

  • Use the named labels, directions or supplied quantities accurately.
  • Connect the visual evidence to the scientific mechanism or calculation.
  • State the relevant model conditions or limitation.

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