Washington Comprehensive Assessment of Science — Grade 8

A student burns a 12-gram piece of magnesium ribbon in a sealed flask containing 8 grams of oxygen gas. A bright white flash occurs, producing magnesium oxide powder. What is the total mass of the contents inside the sealed flask after the reaction?

• A20 grams.
• B12 grams.
• C8 grams.
• D4 grams.

A 1,000-kg car accelerates from 10 meters per second to 20 meters per second. How does the car's kinetic energy change when its velocity doubles?

• AThe kinetic energy quadruples (increases by 4 times).
• BThe kinetic energy doubles (increases by 2 times).
• CThe kinetic energy remains unchanged.
• DThe kinetic energy drops to zero.

A swimmer pushes backward against the pool wall with her feet with a force of 200 Newtons. According to Newton's Third Law, what force does the pool wall exert on the swimmer's feet?

• A200 Newtons forward in the opposite direction.
• B100 Newtons backward in the same direction.
• C0 Newtons because inanimate walls cannot exert forces.
• D400 Newtons upward toward the sky.

A student observes microscopic cells under a microscope and identifies chloroplasts and a rigid cell wall. Which type of cell is the student observing?

• AA plant cell.
• BA human cheek animal cell.
• CA mammalian red blood cell.
• DA nerve neuron cell.

Which statement correctly contrasts the outcome of mitosis with meiosis in multicellular organisms?

• AMitosis creates 2 genetically identical daughter cells, while meiosis creates 4 genetical…
• BMitosis creates 4 gametes, while meiosis creates 2 identical body cells.
• CMitosis doubles chromosome count, while meiosis destroys all DNA.
• DMitosis occurs only in single-celled viruses.

In a population of peppered moths living near industrial towns, dark-colored moths became more common than light-colored moths over several decades. What drove this evolutionary shift?

• ASoot covered tree trunks, giving dark moths better camouflage against bird predators and…
• BLight moths decided to change their gene sequences intentionally to match dark bark.
• CDark moths ate soot, which chemically turned their offspring black.
• DBird predators preferred eating dark moths because dark moths tasted better.

The Cascade Mountain Range in Washington (including Mount Rainier and Mount St. Helens) was formed by which tectonic plate interaction?

• ASubduction at a convergent plate boundary where an oceanic plate slides beneath a contine…
• BSeafloor spreading at a mid-ocean divergent boundary.
• CTransform sliding along the San Andreas fault line.
• DMeteor impact cratering forming volcanic cones.

Which celestial alignment produces a total lunar eclipse?

• ASun – Earth – Moon (Earth is directly between the Sun and Moon).
• BSun – Moon – Earth (Moon is directly between the Sun and Earth).
• CEarth – Sun – Moon (Sun is directly between Earth and Moon).
• DMoon – Sun – Earth (Sun is between Moon and Earth).

A geologist examines five horizontal, undisturbed sedimentary rock layers in a canyon wall. According to the Law of Superposition, where is the oldest rock layer located?

• AAt the very bottom of the rock formation.
• BAt the top of the canyon wall.
• CIn the middle layer containing dinosaur fossils.
• DAge is identical across all five rock layers.

A city requests design proposals for a new pedestrian footbridge. The bridge must span 30 meters, support up to 5,000 kg, and cost under $150,000. In this engineering challenge, what is the $150,000 budget limit called?

• AA constraint.
• BA criterion.
• CA hypothesis.
• DA variable.

A student dissolves ammonium nitrate crystals in water inside a beaker. The digital thermometer reading drops from 22°C to 11°C. What type of reaction occurred?

• AAn endothermic reaction that absorbed thermal energy from the surrounding water.
• BAn exothermic reaction that released heat into the surrounding air.
• CA nuclear fusion reaction that destroyed nitrogen atoms.
• DA phase change that created solid ice out of ammonium.

A neutral atom of Carbon has an atomic number of 6 and a mass number of 12. How many protons, neutrons, and electrons does this neutral Carbon atom contain?

• A6 protons, 6 neutrons, and 6 electrons.
• B12 protons, 6 neutrons, and 6 electrons.
• C6 protons, 12 neutrons, and 12 electrons.
• D0 protons, 6 neutrons, and 6 electrons.

A 5-kg box on a frictionless surface is pulled to the right with a force of 25 Newtons and pulled to the left with a force of 10 Newtons. What is the acceleration of the box?

• A3 meters per second squared to the right.
• B7 meters per second squared to the left.
• C5 meters per second squared to the right.
• D35 meters per second squared to the left.

Which plant vascular tissue is responsible for transporting water and dissolved minerals upward from roots to leaves?

• AXylem.
• BPhloem.
• CStomata.
• DEpidermis.

In pea plants, purple flower color (P) is dominant over white flower color (p). If two heterozygous purple pea plants (Pp x Pp) are crossed, what probability percentage of offspring will have white flowers?

• A25%.
• B50%.
• C75%.
• D100%.

In which cell organelle does cellular respiration take place to convert glucose food energy into usable ATP energy?

• AMitochondria.
• BRibosomes.
• CVacuoles.
• DGolgi apparatus.

What heat transfer mechanism in Earth's mantle drives the slow movement of tectonic plates across Earth's surface?

• AConvection currents in the mantle.
• BRadiation from the Moon.
• CConduction through atmospheric clouds.
• DMagnetic repulsion from solar flares.

A granite igneous rock deep underground is subjected to extreme heat and pressure without melting completely. Into which rock type will the granite transform?

• AMetamorphic rock (gneiss).
• BSedimentary rock (sandstone).
• CExtrusive basalt lava.
• DEvaporite salt deposit.

How do elevated levels of carbon dioxide in the atmosphere contribute to global climate warming?

• ACarbon dioxide absorbs infrared heat radiated from Earth's surface and traps it in the lo…
• BCarbon dioxide reflects all incoming sunlight back into outer space.
• CCarbon dioxide destroys nitrogen molecules, creating friction in air.
• DCarbon dioxide increases the speed of Earth's rotation.

Automotive engineers test two bumper materials: Steel Bumper X absorbs high crash energy but adds 150 kg of weight. Composite Bumper Y is lightweight and improves gas mileage, but absorbs 20% less crash energy. How should engineers approach this decision?

• AEvaluate trade-offs between vehicle safety criteria and fuel efficiency constraints to op…
• BSelect Bumper X and ignore vehicle weight limits.
• CSelect Bumper Y and eliminate all crash safety testing.
• DCancel vehicle manufacturing completely.

Which wave type can travel across the empty vacuum of interstellar space between stars?

• ALight waves (electromagnetic radiation).
• BSound waves from stellar explosions.
• CSeismic S-waves from earthquake faults.
• DOcean tsunami water waves.

A sound wave travels through air at 340 meters per second. If the frequency of the sound wave increases from 170 Hz to 340 Hz, what happens to its wavelength?

• AThe wavelength decreases by half (from 2.0 meters to 1.0 meter).
• BThe wavelength doubles (from 2.0 meters to 4.0 meters).
• CThe wavelength quadruples.
• DThe wavelength remains unchanged at 10 meters.

Why are digital signals (binary code 0s and 1s) preferred over continuous analog signals for long-distance telecommunications?

• ADigital signals can be filtered to eliminate background noise and copied without distorti…
• BDigital signals travel faster than the speed of light in a vacuum.
• CAnalog signals require zero electricity to transmit.
• DDigital signals can only be transmitted through wooden wires.

If a point mutation changes a single base pair in a gene's DNA sequence, what is the most direct consequence for the cell?

• AThe mutated gene may produce an mRNA codon that codes for a different amino acid, alterin…
• BThe cell immediately converts into a plant chloroplast.
• CAll carbohydrates inside the cell are destroyed instantly.
• DThe nuclear membrane disappears and turns into rock.

A population of trout in a Washington mountain stream grows rapidly for three years, then stabilizes around 400 individuals. What ecological principle explains why the population stopped growing?

• AThe stream reached its carrying capacity due to limiting factors like food availability a…
• BTrout stopped reproducing because water temperature reached boiling point.
• CTrout transformed into terrestrial mammals.
• DThe trout population ran out of atmospheric gravity.

What causes prevailing winds and major ocean currents in the Northern Hemisphere to curve to the right instead of moving in a straight line?

• AThe Coriolis effect produced by Earth's rotation on its axis.
• BGravitational pull from the Moon's shadow.
• CMagnetic repulsion from the North Magnetic Pole.
• DHeat radiation from deep ocean volcanic trenches.

A canyon wall shows five undisturbed horizontal sedimentary layers. A vertical body of igneous rock cuts upward across all five layers. What can a geologist conclude about the age of the igneous rock?

• AIt is younger than all five sedimentary layers, because a feature that cuts across layers…
• BIt is older than all five sedimentary layers, because igneous rock always forms before se…
• CIt is the same age as the bottom layer, because both are found deepest in the canyon wall.
• DIts age cannot be compared with the layers, because igneous and sedimentary rocks form in…

Structural engineers use computer software simulations to model how a high-rise building in Seattle will respond to a magnitude 7.5 earthquake. What is the primary advantage of using computer simulations over physical testing?

• AEngineers can safely test extreme disaster scenarios and iterate design improvements quic…
• BComputer simulations eliminate the need for mathematical equations.
• CSimulations guarantee that real earthquakes will never strike the building.
• DComputer models cost zero dollars and require no engineering expertise.

Why do Sodium (Na) and Potassium (K) share very similar chemical reactivity properties (both react violently with water)?

• AThey are in the same vertical Group (Group 1) on the periodic table and have 1 valence el…
• BThey have identical atomic numbers and masses.
• CThey are both noble gases that do not form chemical bonds.
• DThey are located in the same horizontal Period.

If the distance between Earth and the Moon were suddenly reduced to half of its current value, what would happen to the gravitational attraction force between them?

• AThe gravitational force would increase to 4 times its current strength.
• BThe gravitational force would decrease to half its current strength.
• CThe gravitational force would remain completely unchanged.
• DThe gravitational force would drop to zero.

In a Washington freshwater lake, green algae capture 10,000 Joules of solar energy. According to the 10% energy transfer rule in ecology, how much energy is transferred to minnows (primary consumers) that eat the algae?

• A1,000 Joules.
• B10,000 Joules.
• C5,000 Joules.
• D10 Joules.

A strawberry plant sends out a horizontal runner stem that grows a new plantlet. What is a key characteristic of offspring produced through this form of asexual reproduction?

• AThe offspring plantlet is genetically identical to the parent plant.
• BThe offspring plantlet has double the chromosome count of the parent.
• CThe offspring plantlet requires cross-pollination by bees to survive.
• DThe offspring plantlet inherits traits from two different parent plants.

Humans, whales, dogs, and bats all possess forelimbs with similar anatomical bone arrangements (humerus, radius, ulna, carpals), despite using them for swimming, flying, running, or grasping. What does this anatomical similarity indicate?

• AThese mammals inherited a basic limb skeletal structure from a common ancestral species.
• BWhales and bats evolved forelimb bones from plastic ocean debris.
• CForelimb bones are formed by atmospheric weather patterns.
• DThese species choose their own bone shapes based on food preferences.

An air mass originates over the cold North Pacific Ocean and moves inland across western Washington. What temperature and humidity characteristics will this maritime polar (mP) air mass possess?

• ACool temperature and high humidity (moist).
• BHot temperature and low humidity (dry).
• CSub-zero temperature and dry desert air.
• DWarm temperature and zero moisture.

A metal pot of soup sits on an electric stovetop burner. Heat transfers from the hot burner directly into the bottom metal pot surface by which mechanism?

• AConduction.
• BConvection.
• CRadiation.
• DTranspiration.

A straight pencil placed in a glass of water appears bent or broken at the water line when viewed from the side. What wave behavior causes this visual distortion?

• ARefraction (light changes speed as it moves between air and water).
• BReflection (light bounces off the pencil like a mirror).
• CDiffraction (light bends around the rim of the glass).
• DAbsorption (the pencil absorbs all incoming light rays).

A root hair cell absorbs nitrate ions from soil water where nitrate concentration is low, moving them into the cell cytoplasm where nitrate concentration is high. Which cell process is being performed?

• AActive transport (requiring ATP energy).
• BSimple passive diffusion.
• COsmosis.
• DPhotosynthesis.

Building a 6-lane highway through a large forest splits wildlife populations into smaller isolated groups. How does this habitat fragmentation affect native animal species?

• AIt restricts animal movement, decreasing genetic diversity and increasing vulnerability t…
• BIt doubles biodiversity by creating two brand-new animal species overnight.
• CIt eliminates the need for animals to find food.
• DIt increases forest tree growth by converting car exhaust into granite.

Symmetrical patterns of magnetic polarity stripes recorded in basalt rock on both sides of the Juan de Fuca mid-ocean ridge provide key evidence for which geological theory?

• ASeafloor spreading and plate tectonics.
• BMeteor impact cratering forming ocean basins.
• CAtmospheric cloud formation driving moon phases.
• DGlaciers carving out deep ocean trenches.

Which gravitational interaction primarily causes the daily rise and fall of ocean tides along the Washington coastline?

• AGravitational pull exerted on Earth's oceans by the Moon.
• BMagnetic repulsion between Earth's core and sea salt.
• CWind friction from seasonal tornadoes.
• DNuclear radiation from deep ocean hydrothermal vents.

A student tests a liquid sample with universal indicator paper and finds a pH value of 2. How is this solution classified?

• AStrong acid.
• BNeutral liquid.
• CStrong base (alkaline).
• DDistilled pure water.

A 2-kg rock rests on a cliff ledge 10 meters above the ground. If the rock is moved to a higher ledge 30 meters above the ground, what happens to its gravitational potential energy?

• AIts gravitational potential energy triples.
• BIts gravitational potential energy drops to zero.
• CIts gravitational potential energy decreases by half.
• DIts mass triples.

Honeybees gather sugar-rich nectar from flowers for food, while transferring pollen grains between blossoms to enable plant fertilization. What type of symbiotic relationship does this represent?

• AMutualism (both species benefit).
• BParasitism (one species benefits, one is harmed).
• CCommensalism (one species benefits, one is unaffected).
• DPredation (one species kills and consumes another).

In genetics, what term describes the observable physical traits of an organism (such as blue eyes, tall height, or purple flowers)?

• APhenotype.
• BGenotype.
• CAllele frequency.
• DKaryotype.

Western Washington (Seattle) receives abundant annual rainfall, while eastern Washington (Yakima) is semi-arid desert. What topographical feature creates this rain shadow effect?

• AThe Cascade Mountain Range blocking moist air masses from moving east without dropping pr…
• BThe Pacific Ocean drying out air before it hits land.
• CEastern Washington being located closer to the equator.
• DLake Washington absorbing all rain clouds from the sky.

What is the ultimate energy source driving volcanic eruptions, earthquakes, and geysers in Yellowstone and the Cascade Range?

• AInternal thermal energy from radioactive decay in Earth's core and mantle.
• BSolar radiation absorbed by surface trees.
• CGravitational pull from Jupiter.
• DFriction from aircraft flying overhead.

During wind tunnel testing, a drone prototype vibrates violently and loses altitude when wind speed reaches 40 km/h. What is the proper engineering action?

• AAnalyze structural vibration data, reinforce frame joints or adjust blade pitch, and re-t…
• BFalsify wind tunnel data and certify the drone for commercial production.
• CIncrease test wind speed to 100 km/h until the drone destroys itself.
• DConclude that aerodynamics is an unprovable myth.