Earth & Space Science — Midterm exam worked answers
Student exam paperAn independent assessment of the core chapters listed below, followed by corrections and discussion.
15 questions · 35 points · suggested 60 minutes
Student instructions
- Suggested time: 60 minutes; allow breaks or accommodations and record them.
- Work independently with a calculator, blank paper and the reference relationships printed in this paper. Grades 9, 11 and 12 may also use the course-linked NYSED reference tables. Use no lesson notes or answer key during an assessed attempt.
- Show reasoning and units for written tasks. All supplied datasets are illustrative; do not present them as measurements you collected.
- Objective items: 1 point each. Written items: 3 points each, one per criterion. A parent or teacher marks the written work; the app never grades an explanation automatically.
- Sample exam: try the whole paper before opening the worked key, then revisit the linked chapters. The sample and final are different papers; this is a course assessment, not an official Regents examination.
Reference relationships
| Relationship or tool | Conditions |
|---|---|
| Maps and budgets | Gradient=elevation change/horizontal distance; storage change=inputs−outputs. |
| Radioactive decay | Remaining parent fraction=(½)ⁿ; age=n×half-life under the stated dating assumptions. |
| Orbital ratios | For one dominant central mass, T²/a³ is constant; compare semimajor axes in the same units. |
| Spectra | Redshift z=(observed wavelength−rest wavelength)/rest wavelength. Match line patterns first. |
| Earth and Space reference tables | Use the linked 2024 NYSED tables: read title, units, legend and conditions; write the table evidence used. |
Coverage and marks
| Chapter | Questions | Points |
|---|---|---|
| Investigating Earth | 1, 2, 3 | 7 |
| Earth’s Interior & Plate Tectonics | 4, 5, 6 | 7 |
| Rocks, Landscapes & Water | 7, 8, 9 | 7 |
| Earth’s History | 10, 11, 12 | 7 |
| Atmosphere & Weather | 13, 14, 15 | 7 |
Parent / teacher marking guide
- Mark objective answers after submission. Written marks remain pending until a parent or teacher applies the three-point criteria.
- Accept scientifically equivalent wording and valid alternative methods. Award stated method credit for a correct model or substitution even if later arithmetic fails.
- A raw percentage describes this paper only; it is not a validated course grade or a certification. Review chapter-level evidence and the learner’s independent explanations.
- Record support and accommodations, save corrections and reassess with different tasks. Do not count copied solutions as independent mastery.
Question 1 · 1 point
Elevation rises 60 m over a horizontal distance of 3 km. Find gradient.
Worked answer
20 m/km
60 ÷ 3 = 20.
1 point for the correct objective answer; no written-method marks for this item.
Question 2 · 3 points
Three rain measurements are 12, 14, and 13 mm. Report a useful summary.
Worked answer
Mean 13 mm, observed range 12–14 mm; the interpretation depends on the sampling method.
Mean = (12 + 14 + 13) ÷ 3 = 13 mm.
The observed range is 12–14 mm.
State the method and whether the values are repeated measurements or different sites.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Mean = (12 + 14 + 13) ÷ 3 = 13 mm.
- 1 point: reach a scientifically supported conclusion: Mean 13 mm, observed range 12–14 mm; the interpretation depends on the sampling method.
Question 3 · 3 points
Evaluate the evidence in this supplied classroom investigation: Build and Evaluate a Landscape Profile. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
The 0.5–1 km segment rises 40 m in 0.5 km, or 80 m/km. The overall rise is 80 m in 2 km, or 40 m/km. Equal endpoint gradients can conceal different steep sections. More closely spaced observations could reveal changes between the sampled points; the profile is also only one line across the landscape.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 4 · 1 point
The mantle is about 2,900 km thick, and the outer core is about 2,200 km thick. How many km thicker is the mantle than the outer core?
Worked answer
700 km
2,900 − 2,200 = 700 km.
1 point for the correct objective answer; no written-method marks for this item.
Question 5 · 3 points
Earth's radius is about 6,371 km, and continental crust averages about 40 km thick. About what percent of Earth's radius is the crust?
Worked answer
Less than 1% of Earth's radius (about 0.6%) — an extremely thin outer skin.
Divide the crust's thickness by Earth's total radius: 40 ÷ 6,371.
40 ÷ 6,371 ≈ 0.0063.
Convert to a percent: 0.0063 × 100 ≈ 0.6%.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Divide the crust's thickness by Earth's total radius: 40 ÷ 6,371.
- 1 point: reach a scientifically supported conclusion: Less than 1% of Earth's radius (about 0.6%) — an extremely thin outer skin.
Question 6 · 3 points
Evaluate the evidence in this supplied classroom investigation: Test a Seafloor-Spreading Model. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
Age increases symmetrically away from the ridge. On one side, 120 km / 6 Ma = 20 km/Ma = 2 cm/year; opposite sides separate at 4 cm/year in this ideal model. The pattern supports new crust forming at the ridge. Magnetic-stripe symmetry and independent motion measurements would add evidence. Average ages cannot establish the speed at every instant.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 7 · 1 point
A mineral breaks apart along smooth, flat surfaces that follow its internal crystal structure. This property is called…
- fracture
- cleavage
- luster
- streak
Worked answer
cleavage
Breaking along smooth, flat planes that follow the crystal structure is cleavage; uneven, rough breakage is called fracture.
1 point for the correct objective answer; no written-method marks for this item.
Question 8 · 3 points
A mystery mineral scratches a piece of calcite, but a piece of fluorite scratches the mystery mineral. Between which two Mohs hardness numbers must the mystery mineral's hardness fall?
Worked answer
Between 3 and 4 on the Mohs scale.
Calcite has a Mohs hardness of 3. Since the mystery mineral scratches calcite, the mystery mineral must be harder than 3.
Fluorite has a Mohs hardness of 4. Since fluorite scratches the mystery mineral, fluorite must be harder than the mystery mineral — so the mystery mineral is softer than 4.
Combining both clues: the mystery mineral's hardness is greater than 3 and less than 4.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Calcite has a Mohs hardness of 3. Since the mystery mineral scratches calcite, the mystery mineral must be harder than 3.
- 1 point: reach a scientifically supported conclusion: Between 3 and 4 on the Mohs scale.
Question 9 · 3 points
Evaluate the evidence in this supplied classroom investigation: Account for Water in a Landscape Model. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
Mean runoff falls from 84 to 27 mL, a reduction of (84−27)/84 × 100 ≈ 67.9%. Water entering soil can remain stored, evaporate, be used by plants, or move deeper; infiltration alone does not measure aquifer recharge. A small tray does not reproduce field soils, large storms, or saturated conditions.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 10 · 1 point
Which era/nickname pairing is correct?
- Mesozoic — age of reptiles
- Cenozoic — age of reptiles
- Paleozoic — age of mammals
- Precambrian — age of dinosaurs
Worked answer
Mesozoic — age of reptiles
The Mesozoic era is nicknamed 'the age of reptiles' because dinosaurs and other reptiles dominated it.
1 point for the correct objective answer; no written-method marks for this item.
Question 11 · 3 points
If Earth's entire 4.6-billion-year history were squeezed into one 365-day calendar year (starting January 1), around what date would the mass extinction that ended the dinosaurs — about 66 million years ago — fall on?
Worked answer
About December 26 — the dinosaurs' extinction happened in just the final week of the 'Earth year,' with humans not appearing until the last minutes of December 31.
Set up a ratio comparing the event's age to Earth's total age: 66,000,000 ÷ 4,600,000,000.
Divide: 66,000,000 ÷ 4,600,000,000 ≈ 0.0143 — that's the fraction of the model year that has passed since the event.
Multiply that fraction by the 365 days in the model year: 0.0143 × 365 ≈ 5.2 days.
The event happened about 5.2 days before the end of the year (December 31), so count backward: December 31 − 5 days ≈ December 26.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Set up a ratio comparing the event's age to Earth's total age: 66,000,000 ÷ 4,600,000,000.
- 1 point: reach a scientifically supported conclusion: About December 26 — the dinosaurs' extinction happened in just the final week of the 'Earth year,' with humans not appearing until the last minutes of December 31.
Question 12 · 3 points
Evaluate the evidence in this supplied classroom investigation: Model Radioactive Decay and Date an Event. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
The ideal curve describes an expected population, so it can have fractional counts. A real trial fluctuates and has whole counters. Under suitable initial-parent/daughter and closed-system assumptions, 25% parent implies two half-lives, or 20 Ma since the mineral’s dating clock began, often crystallization or cooling. Inherited grains can be older than their deposition. Counter rounds illustrate probability, not the physics of nuclear transformation.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 13 · 1 point
Rising air cools, and water vapor changes into the tiny liquid droplets that form clouds. What is this process called?
- Precipitation
- Condensation
- Runoff
- Evaporation
Worked answer
Condensation
Condensation happens when rising, cooling air causes water vapor to turn back into liquid droplets, forming clouds.
1 point for the correct objective answer; no written-method marks for this item.
Question 14 · 3 points
Starting with ocean water, put the water cycle in order through evaporation, condensation, and precipitation as rain over a mountain range. Name what drives each step.
Worked answer
Ocean water evaporates (sun) → water vapor condenses into clouds → precipitation falls as rain over the mountains → runoff flows back downhill toward the ocean (gravity).
Start at the ocean: the sun's energy heats the surface water until it evaporates into invisible water vapor that rises into the atmosphere. (Driven by the sun.)
As the vapor rises and drifts inland on the wind, it cools and condenses into tiny liquid droplets that cluster together as clouds. (Driven by cooling air, made possible by the sun's earlier heating.)
The droplets in the clouds keep colliding and growing as the clouds are pushed toward the mountains, until they're heavy enough to fall as precipitation — rain. (Driven by gravity.)
The rain that doesn't soak into the ground runs downhill as runoff, collecting into streams that flow back toward the ocean. (Driven by gravity.)
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Start at the ocean: the sun's energy heats the surface water until it evaporates into invisible water vapor that rises into the atmosphere. (Driven by the sun.)
- 1 point: reach a scientifically supported conclusion: Ocean water evaporates (sun) → water vapor condenses into clouds → precipitation falls as rain over the mountains → runoff flows back downhill toward the ocean (gravity).
Question 15 · 3 points
Evaluate the evidence in this supplied classroom investigation: Make and Revise a Weather Forecast. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
Cooling from 23°C to 16°C, a wind shift from SW to NW, and rising pressure after showers are consistent with a cold front. A forecast of cooler conditions and possible clearing is supported by the final row, but exact timing and local rain depend on moisture and other conditions. Pressure alone cannot show whether enough moist air will rise and condense.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.