Science 6: Matter, Energy & Earth Systems — Final Exam worked answers
Student exam paperOriginal Grade 6 home-study paper with complete supplied scenarios, calculations, and scientific explanation. It samples the course and does not replace review of the investigation notebook.
40 questions · 120 points · suggested 135 minutes
Student instructions
- Work independently after agreeing timing and access support with a parent; record any support used.
- All scenario numbers and records are illustrative. Use the stated assumptions and do not invent missing data.
- Use the reference relationships below and a basic calculator when helpful. Show a calculation, retain units, and explain what it means.
- For concept questions, connect a claim with the relevant mechanism or evidence and a specific limit. A supported alternative can satisfy the criteria.
- Keep the answer key and lesson models closed during an independent attempt. Discuss corrections after human marking.
- Use saved investigation plans, observations, revised models, projects, and an oral conference as additional assessment evidence.
Measurement and model relationships
| Relationship | How to use it |
|---|---|
| Length | 10 mm = 1 cm; 100 cm = 1 m |
| Mass and volume | 1,000 g = 1 kg; 1,000 mL = 1 L |
| Mean | Sum comparable values and divide by their count |
| Density | Mass ÷ volume; preserve units such as g/mL or g/cm³ |
| Percentage | Part ÷ stated whole × 100; identify the denominator |
| Change/rate | Ending minus starting value; divide a stated change by its time interval |
| Tidal range | High water minus low water with the same reference |
| Space scale | Actual stated distance ÷ actual km per model cm |
| Energy account | Include relevant stores and transfers; °C is not a joule value |
Coverage and marks
| Chapter | Questions | Points |
|---|---|---|
| Chapter 1 · Inquiry, Measurement & Models | 1, 2, 3, 4, 5 | 15 |
| Chapter 2 · Matter, Mixtures & Water Properties | 6, 7, 8, 9, 10 | 15 |
| Chapter 3 · Energy, Heat & Thermal Design | 11, 12, 13, 14, 15 | 15 |
| Chapter 4 · Electricity, Magnetism & Light | 16, 17, 18, 19, 20 | 15 |
| Chapter 5 · Earth Systems, Plates & Earth Materials | 21, 22, 23, 24, 25 | 15 |
| Chapter 6 · Water, Air, Weather & Climate | 26, 27, 28, 29, 30 | 15 |
| Chapter 7 · Ecosystems, Watersheds & Conservation | 31, 32, 33, 34, 35 | 15 |
| Chapter 8 · Earth, Moon, Sun & Space Models | 36, 37, 38, 39, 40 | 15 |
Parent / teacher marking guide
- Each written task has three separate one-point criteria. Award for meaning and reasoning, not keyword matching.
- A different accurate supported answer may receive full credit. Do not require personal or political agreement.
- Keep written marks pending until reviewed by a person. Record the criteria met and one improvement.
- Compare exam evidence with the notebook and project process rather than certify mastery from one total.
Question 1 · 3 points
A pictured plant has four wilted leaves. A caption says “lack of fertilizer caused the wilting.” Distinguish observation and inference, and name evidence that could test the explanation.
Worked answer
Four wilted leaves is the stated observation. Lack of fertilizer is a proposed cause; water, heat, disease, and other factors could matter. A comparable investigation or additional condition records should distinguish the proposed cause from alternatives.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Identify the observation.
- 1 point: Identify the unestablished cause inference.
- 1 point: Propose relevant additional evidence or a fair test.
Question 2 · 3 points
A wide paper strip is tested across a 12 cm gap; a narrow strip across an 8 cm gap. The wide strip holds more identical counters. Explain the fair-test problem and a corrected design.
Worked answer
Strip width and support gap both differ. The gap can affect bending, so counter load does not isolate width. Use matched gap, material, length, placement, and failure rule, then repeat fresh strips while varying width.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Name both changed factors.
- 1 point: Explain why the causal conclusion is limited.
- 1 point: Specify a corrected matched/repeated comparison.
Question 3 · 3 points
A ruler records an object from 1.5 cm to 7.8 cm. Find its length in centimeters and millimeters, then explain why 6.300000 cm is not automatically more reliable.
Worked answer
Length is 7.8 − 1.5 = 6.3 cm, or 63 mm. Additional zeros do not improve the ruler’s resolution, alignment, or reading method; keep precision consistent with the evidence.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Find 6.3 cm by subtracting the start.
- 1 point: Convert to 63 mm.
- 1 point: Explain the precision or method limit.
Question 4 · 3 points
Comparable trial loads are 9, 12, and 15 counters. Calculate the mean and range. The fourth entry is missing: explain why it must not become zero.
Worked answer
The mean is 36 ÷ 3 = 12 counters; the range is 9–15. The absent fourth entry is not an observed zero and should stay missing. Counting it as zero would invent evidence and distort the summary.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate mean 12 counters.
- 1 point: Give range 9–15 or span 6 with context.
- 1 point: Distinguish missing data from measured zero.
Question 5 · 3 points
A sealed 120 g water sample cools from 32 to 24 °C without measured mass change. Explain the matter and energy boundaries and one missing quantity.
Worked answer
The sample keeps its modeled water matter while energy can transfer to cooler surroundings. Sealed does not mean perfectly insulated. The 8 °C drop is not 8 J; an energy calculation requires a stated material/amount model and further information.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Explain matter retained under the stated boundary.
- 1 point: Explain energy can cross the boundary.
- 1 point: Distinguish temperature change from joules or another specific limit.
Question 6 · 3 points
A closed 70 g ice sample melts into liquid water with the same mass. Describe particle arrangement, motion, and conservation without saying particles become larger.
Worked answer
Solid water particles vibrate within a more constrained arrangement; liquid particles remain close but move past one another. The same water remains within the closed boundary, so mass is conserved. State change does not require particles to become larger or cease to exist.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Compare solid and liquid arrangement/motion.
- 1 point: Account for the same closed-sample mass.
- 1 point: Correct particle-growth or motionless-solid misconception.
Question 7 · 3 points
Samples P and Q are the same modeled material at matched conditions. P is 18 g and 6 cm³; Q is 45 g and 15 cm³. Compare density and explain why size is not the definition.
Worked answer
Both densities are 3 g/cm³: 18 ÷ 6 and 45 ÷ 15. Q has greater mass and volume but the same ratio. Density is mass per volume under stated conditions, not simply heaviness or sample size.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate P as 3 g/cm³.
- 1 point: Calculate Q as 3 g/cm³.
- 1 point: Explain the ratio and size distinction.
Question 8 · 3 points
A stated open reaction starts with 90 g inside a vessel and ends with 84 g after 6 g gas leaves. Explain conservation and why bubbles alone would be weaker chemical evidence.
Worked answer
84 + 6 = 90 g accounts for the material inside and the gas transferred out. Matter was not destroyed. Bubbles alone can also occur in boiling or release of existing gas, so substance/process evidence is needed before inferring a chemical change.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Account for 90 g across the boundary.
- 1 point: Explain gas transfer rather than destruction.
- 1 point: Give a nonchemical bubble possibility or identity-evidence requirement.
Question 9 · 3 points
A model mixture has 80 g water, 4 g dissolved salt, and 2 g sand. A suitable filter removes all the sand. Find the filtrate mass and explain what remains and what cannot be concluded about safety.
Worked answer
The filtrate is 84 g: water plus dissolved salt. Dissolved particles remain rather than vanish or be trapped automatically by this filter. Clearer appearance does not certify removal of microbes or other dissolved substances and cannot establish drinking safety.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 84 g.
- 1 point: Explain salt remains dissolved with water.
- 1 point: Reject a clarity/filtration-only safety conclusion.
Question 10 · 3 points
Use modeled water density 1 g/mL. Object A is 15 g and 30 mL; B is 15 g and 5 mL. Calculate densities and explain why a hollow shape or surface support may need a different account.
Worked answer
A is 0.5 g/mL and B is 3 g/mL, so equal mass does not mean equal average density. Hollow geometry and enclosed air affect displacement/whole-object density; surface tension can matter for very small objects. These require a mechanism beyond largest always sinks.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate A as 0.5 g/mL.
- 1 point: Calculate B as 3 g/mL.
- 1 point: Explain geometry, displacement, or surface-force qualification.
Question 11 · 3 points
A book rests on a high shelf; a toy rolls along the floor; a battery-powered lamp emits light. Name relevant energy descriptions and distinguish energy from matter or temperature.
Worked answer
The book–Earth system has gravitational potential energy relative to a stated reference; the rolling toy has kinetic energy; the lamp transfers energy through electrical and radiation/thermal pathways. Joules describe energy, while grams and °C describe other quantities.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Identify potential and kinetic examples accurately.
- 1 point: Explain a battery/lamp energy pathway.
- 1 point: Distinguish energy from matter or temperature units.
Question 12 · 3 points
A model receives 150 J, with 45 J visible light and 90 J thermal output recorded. Calculate the unaccounted amount and light fraction; explain whether missing energy can be declared destroyed.
Worked answer
The listed outputs total 135 J, leaving 15 J unaccounted for. Light is 45 ÷ 150 = 30% of input. Check omitted pathways, storage, or measurement limits rather than declare energy destruction.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 15 J unaccounted.
- 1 point: Calculate 30% light fraction.
- 1 point: Explain an incomplete account rather than destruction.
Question 13 · 3 points
Two samples of the same water state are at 28 °C, with volumes 60 and 240 mL. Both sit in a 20 °C room. Explain equal temperature, total energy comparison, and net heat-transfer direction.
Worked answer
Equal temperature does not mean equal total thermal energy; the larger matched-material amount generally has more under the same reference. Both are warmer than the room, so net heat transfer tends outward. The temperature reading is not a joule total.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Distinguish equal temperature from total energy.
- 1 point: Use amount/material to qualify the comparison.
- 1 point: Predict outward net transfer to cooler surroundings.
Question 14 · 3 points
A warm cup transfers energy through its wall, nearby circulating air, and infrared radiation. Identify each mechanism and correct “all heat must rise.”
Worked answer
Wall transfer through local interactions is conduction; moving air carrying energy is convection; infrared exchange is radiation. Rising warm fluid is a buoyancy situation, not a rule for all mechanisms or directions.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Identify conduction and convection correctly.
- 1 point: Identify radiation.
- 1 point: Correct the universal upward-direction claim.
Question 15 · 3 points
Matched ten-minute drops: sleeve P, 4, 5, 6 °C at 3 tokens; Q, 2, 3, 4 °C at 6 tokens. Desired mean is at most 5 °C and budget at most 4 tokens. Recommend with evidence and a retest limit.
Worked answer
P averages 5 °C and meets the three-token cost within budget. Q averages 3 °C but exceeds the cost constraint. Recommend P under the stated problem; repeat for consistency or retest a cheaper Q redesign rather than inherit old results.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate means 5 and 3 °C.
- 1 point: Apply performance and budget together.
- 1 point: State a justified repeat/redesign requiring evidence.
Question 16 · 3 points
Two neutral objects each have 12 positive and 12 negative model units. Three negative units move from A to B. Find net imbalances and explain the combined charge account.
Worked answer
A has 12 positive and 9 negative, net positive three; B has 12 positive and 15 negative, net negative three. The combined 24 positive and 24 negative units remain; charge transferred rather than being created.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Find A net positive three.
- 1 point: Find B net negative three.
- 1 point: Explain conserved combined charge and model units.
Question 17 · 3 points
In an ideal parallel model, A’s branch switch is open and B’s branch and common path are closed. Predict lamps and explain what would happen if the common path opened.
Worked answer
A is off, while B remains on because its loop is complete. Opening the common path interrupts both branches and stops both. The lamp receives energy; it does not use up the returning charge.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Predict A off and B on.
- 1 point: Explain common-path opening stops both.
- 1 point: Trace paths or distinguish energy from charge consumption.
Question 18 · 3 points
A magnet holds 6, 5, and 7 identical clips in repeated trials at one gap. At a larger gap it holds 2. Calculate the repeat mean and explain what the comparison does not measure.
Worked answer
The repeated mean is 6 clips, with variation 5–7. Lower count at the larger gap supports a weaker holding outcome under the stated method. Count is a proxy, not force in newtons, and it does not establish an exact distance law or zero field beyond the gap.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate mean 6 clips.
- 1 point: Describe the distance-related outcome with matched-method context.
- 1 point: Identify proxy, variation, or precise-law limit.
Question 19 · 3 points
An incident ray is 25° from the perpendicular normal at an ideal plane mirror. Give the reflected normal and surface angles, then explain how a book can be seen without emitting its own light.
Worked answer
The reflected ray is 25° from the normal and 65° from the surface. A book scatters some incoming light toward the eye, so it need not emit light to be visible.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Give normal angle 25°.
- 1 point: Give surface angle 65° with correct reference.
- 1 point: Explain reflected source–object–eye light.
Question 20 · 3 points
An air-to-water ray enters at 45° from the normal and continues at 28°. Another ray arrives exactly along the normal. Explain both directions and why white-light and red-only views of a model green card can differ.
Worked answer
The first bends toward the normal, since 28° is smaller. The normal-incidence ray can change speed without sideways bending. A card reflecting only green in the model can look green under white light but dark under red-only light because no green component is supplied.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Interpret oblique bending toward the normal.
- 1 point: Explain no sideways bend at normal incidence.
- 1 point: Connect observed color with source and material.
Question 21 · 3 points
A modeled 75 mL rainfall arrival is divided into 30 mL runoff, 25 mL infiltration, 10 mL leaf interception, and 10 mL pond storage. Check the account and connect three Earth spheres.
Worked answer
The destinations sum to 75 mL. Rain links atmosphere/hydrosphere; infiltration connects water and geosphere; interception involves biosphere. The record is one interval; later uptake or evaporation would need additional accounting.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Check the 75 mL total.
- 1 point: Link at least three spheres through labeled processes.
- 1 point: State the bounded-interval or omitted-pathway limit.
Question 22 · 3 points
Correct “plates float on a liquid mantle, and the inner core must be liquid because it is hotter.” Include one indirect evidence method.
Worked answer
Most mantle rock is solid but can deform slowly; plates are lithosphere, not only crust. The outer core is liquid and inner core solid, with pressure and composition as well as temperature affecting state. Earthquake-wave behavior is one indirect evidence method.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Correct mantle/plate classification.
- 1 point: Correct core state using pressure or composition.
- 1 point: Name and explain relevant indirect evidence.
Question 23 · 3 points
Two plate markers increase their separation from 250 to 265 cm in five years. A ridge lies between them in the supplied map. Calculate the relative rate and explain a supported inference and limit.
Worked answer
Separation increases 15 cm in five years, giving 3 cm/year mean relative separation. The ridge supports a divergent-boundary interpretation. It does not give each plate’s individual speed or predict a precise future earthquake.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 3 cm/year relative rate.
- 1 point: Connect increased separation/ridge with divergence.
- 1 point: State individual-speed or future-event limit.
Question 24 · 3 points
A key lists A: metallic luster/pale streak; B: nonmetallic luster/dark streak; C: nonmetallic luster/pale streak. An unknown is nonmetallic with dark streak. Give its best key match and explain two identification limits.
Worked answer
B matches the stated two properties within the key. The limited candidate set and observation/test quality prevent claiming a universal unique identity. Color, scratch behavior, or other appropriate evidence could strengthen the match; do not improvise unsafe testing.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Select B with both matching properties.
- 1 point: Name the candidate-list or incomplete-property limit.
- 1 point: Name method quality or a relevant additional property.
Question 25 · 3 points
A rock changes while solid under heat/pressure, later weathers, is carried by a stream, and settles. Name the rock change and the three later processes, and explain why a fixed cycle is unnecessary.
Worked answer
The solid heat/pressure change is metamorphism. Breakdown is weathering, transport erosion, and settling deposition. Conditions permit several later pathways, so the rock need not pass through every category in one fixed order.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Identify metamorphism without complete melting.
- 1 point: Distinguish weathering, erosion, and deposition.
- 1 point: Explain branching rather than a compulsory cycle.
Question 26 · 3 points
A modeled area receives 65 mm water during a week. Runoff is 20 mm, evaporation/transpiration 18 mm, and storage increases 27 mm. Check the account and name two different drivers or processes.
Worked answer
20 + 18 + 27 = 65 mm, balancing the stated input. Solar/surrounding energy supports evaporation or transpiration, while gravity contributes to rainfall/runoff. Storage increase is not an outgoing flow, and the model does not include every possible groundwater exchange.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Check the 65 mm account.
- 1 point: Explain energy and gravity roles or two distinct pathways.
- 1 point: Preserve storage/boundary or alternative-path limit.
Question 27 · 3 points
A fictional noon weather record gives 16 °C and 1,008 hPa with 5 mm rain over the previous 24 hours. Explain why this is not a daily maximum, a guaranteed forecast, or a regional climate record.
Worked answer
The temperature is one noon observation, not a maximum over all hours. The rainfall measures a completed stated interval, not a future prediction. One local day does not establish long-term regional climate; method, duration, and spatial coverage matter.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Distinguish noon from daily maximum.
- 1 point: Distinguish observation from prediction.
- 1 point: Explain the climate-scale/coverage limit.
Question 28 · 3 points
Matched fictional sites are at 1,021 and 1,012 hPa. In a model omitting rotation and friction, predict the pressure-driven response. Why does a warmed sealed flexible bag not necessarily gain more air?
Worked answer
The difference is 9 hPa and the simplified response is toward lower pressure, with real influences omitted. A flexible sealed bag can expand with the same amount of gas as temperature changes; more volume does not establish added particles.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 9 hPa or correctly identify higher/lower.
- 1 point: Predict response toward lower pressure with a model limit.
- 1 point: Explain fixed amount and changing flexible volume.
Question 29 · 3 points
Three matched long-period seasonal mean records are 13.0, 13.3, and 13.6 °C. A cold day occurs in the last period. Describe the trend and explain why the day and trend can coexist.
Worked answer
The summaries rise 0.6 °C from first to last. The long-period mean does not determine every daily observation. Short-term variability permits cold weather within a warmer distribution; the graph alone does not attribute the cause.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate or state the 0.6 °C rise.
- 1 point: Distinguish weather event from long-term climate summary.
- 1 point: Explain variability or attribution limit.
Question 30 · 3 points
A learner says a warmed closed jar proves greenhouse gases are a solid roof and settles every climate-response choice. Correct the physical model and explain the evidence and policy distinction.
Worked answer
Greenhouse gases interact with infrared radiation, not a solid perfectly sealed roof. A jar also changes convection and other conditions, so it is not a complete atmospheric test. Scientific mechanisms and broader evidence inform response choices, which also need criteria, costs, access, and tradeoffs.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Explain radiation interaction rather than a solid roof.
- 1 point: Identify jar/model or broader-evidence limits.
- 1 point: Separate physical explanation from policy preference and criteria.
Question 31 · 3 points
Equal sampled areas record site A 7 species/24 individuals and site B 4 species/40 individuals. Compare richness and abundance and state one limit to a habitat-quality judgment.
Worked answer
A has greater recorded richness; B has more individuals. Species needs, identity, season, detection, and other conditions affect habitat interpretation. One metric under one survey does not establish universally better habitat or a whole biome.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Compare species richness correctly.
- 1 point: Compare individual abundance correctly.
- 1 point: Explain a sampling or organism-specific quality limit.
Question 32 · 3 points
A stated web has leaves → caterpillar → bird and seeds → mouse → bird. Of 600 modeled resource energy units, 90 enter new consumer biomass. Explain arrows, fraction, and what the remaining energy or a population prediction requires.
Worked answer
Arrows point from food resource toward the recipient. 90 ÷ 600 = 15% in this supplied model. The remaining energy follows other pathways rather than being destroyed, and the web alone lacks population/rate information for exact future counts.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Explain resource-to-consumer arrows.
- 1 point: Calculate modeled 15%.
- 1 point: Identify other energy pathways or quantitative prediction limit.
Question 33 · 3 points
A closed nutrient-store model starts soil 15, plants 10, animals 5 units. Four move soil→plants, three plants→animals, and two animals→soil. Find final stores and distinguish matter from usable energy.
Worked answer
Soil becomes 13, plants 11, and animals 6 units, totaling the original 30. These transfers conserve the modeled nutrient matter. They do not return all original usable energy to plants; energy spreads into other pathways and continued input is needed.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate soil 13 and plants 11.
- 1 point: Calculate animals 6 and conserved total 30.
- 1 point: Distinguish nutrient matter from energy flow.
Question 34 · 3 points
Matched illustrative sediment means are 30 g bare and 18 g buffered. The buffer costs 3 tokens within a 4-token budget. Find relative reduction and give a bounded recommendation with a tradeoff or further test.
Worked answer
Reduction is 12 g, or 12 ÷ 30 = 40%. The buffer fits the stated budget and merits the defined model recommendation. Field scale, storms, maintenance, other ecological outcomes, and access require further evidence; a different feasible proposal can be justified with those criteria.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 12 g and 40% reduction.
- 1 point: Apply the modeled budget and evidence.
- 1 point: State a meaningful tradeoff, scale limit, or follow-up.
Question 35 · 3 points
Matched oxygen records at A are 6, 7, 8 mg/L and at B 3, 4, 5 mg/L. A looks clearer. Compare means and explain why Friday’s missing record and drinking safety need separate treatment.
Worked answer
A averages 7 mg/L and B 4 mg/L. Friday’s absence is not zero oxygen. Clear appearance and these limited oxygen readings do not certify microbial or dissolved-chemical safety or represent every season.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate means 7 and 4 mg/L.
- 1 point: Distinguish missing data from measured zero.
- 1 point: Reject visual/indicator-only drinking or universal quality claims.
Question 36 · 3 points
A bright Moon is visible and a satellite follows a curved Earth path. Correct “the Moon is a star and the satellite has no gravity because it is above air.”
Worked answer
The Moon is visible mainly through reflected sunlight, not star-like emission. Gravity acts beyond the atmosphere and redirects the satellite’s moving path. A simple orbit drawing still needs explicit scale and further speed/distance information for numerical prediction.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Distinguish reflected Moon light from star emission.
- 1 point: Explain gravity and changing orbital direction.
- 1 point: Identify a diagram or numerical-prediction limit.
Question 37 · 3 points
A supplied seasonal model gives 12 daylight hours at 50 energy units per area per hour and another season 8 hours at 30. Calculate daily totals and explain rotation, orbit/tilt, and a weather limit.
Worked answer
Totals are 600 and 240 units per area per day. Earth’s rotation explains daily day/night, while orbit with approximately fixed axial tilt changes seasonal angle/day length. These model totals do not guarantee actual temperature on each day.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate 600 and 240 with per-area daily units.
- 1 point: Distinguish rotation from orbit/tilt mechanisms.
- 1 point: State local-weather or illumination-model limit.
Question 38 · 3 points
An ordinary crescent is observed, then the visible bright fraction grows toward full. Explain the illumination, the growing-fraction term, and why Earth’s shadow is not the ordinary cause.
Worked answer
About half the Moon is sunlit while the Earth observer sees a changing portion as the Moon orbits. The increasing visible fraction is waxing. Ordinary phase geometry does not put the Moon in Earth’s shadow; that requires a special lunar-eclipse alignment.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Explain sunlit-half/viewed-fraction geometry.
- 1 point: Name waxing correctly.
- 1 point: Distinguish ordinary phase from Earth-shadow eclipse.
Question 39 · 3 points
A diagram shows Sun–Earth–Moon aligned with the Moon in shadow. A fictional tide table has high 5.8 and low 1.8 m. Identify the eclipse, find the range, and explain tides’ different mechanism.
Worked answer
The alignment represents a lunar eclipse, with Earth’s shadow on the Moon. The tide range is 4.0 m. Tides involve gravitational differences from Moon/Sun and local ocean response, not that shadow; the fictional table is not a local shore forecast.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Identify lunar eclipse and Earth as shadow caster.
- 1 point: Calculate range 4.0 m.
- 1 point: Explain gravitational tide mechanism or local forecast limit.
Question 40 · 3 points
At 1 cm per 2,000,000 km, a supplied 100,000,000 km distance and 400,000 km distance are pictured as 50 and 8 cm. Audit the values and explain how enlarged symbols could remain useful.
Worked answer
The first is correctly 50 cm. The second should be 0.2 cm or 2 mm, not 8 cm. Enlarged symbols can illustrate relationships if their size/spacing limits are explicit; they cannot support numerical distance claims under an unstated different scale.
Compare each criterion with the learner’s actual reasoning. Accurate supported alternatives may receive full credit. Written answers require human marking.
Marking criteria
- 1 point: Calculate/check 50 cm.
- 1 point: Find 0.2 cm or 2 mm for the second.
- 1 point: Explain honest scale labels and purpose limits.