South Dakota Science Assessment — Grade 8

Which subatomic particles are located in the nucleus of an atom?

• AProtons and neutrons
• BProtons and electrons
• CNeutrons and electrons
• DElectrons only

Elements in the same vertical column (group) of the periodic table share similar chemical properties primarily because they have the same number of:

• AValence electrons
• BNeutrons
• CTotal electron shells
• DProtons

What happens to the total mass of reactants during a chemical reaction in a closed container?

• AIt remains equal to the total mass of the products.
• BIt increases because new atoms are created.
• CIt decreases because matter is converted entirely to energy.
• DIt changes unpredictably depending on temperature.

As a sample of water is heated from 20°C to 80°C, what occurs at the molecular level?

• AThe average kinetic energy of the water molecules increases.
• BThe water molecules expand and increase in mass.
• CThe water molecules stop moving completely.
• DThe chemical bonds between hydrogen and oxygen break to form gas atoms.

Which state of matter has a definite volume but no definite shape?

• ALiquid
• BSolid
• CGas
• DPlasma

According to Newton's first law of motion, an object at rest will remain at rest unless acted upon by:

• AAn unbalanced force
• BA balanced force
• CZero net force
• DGravitational force only

If a net force of 20 N is applied to a 4 kg mass, what is the resulting acceleration?

• A5 m/s²
• B80 m/s²
• C0.2 m/s²
• D16 m/s²

What is the distance between two consecutive crests of a transverse wave called?

• AWavelength
• BAmplitude
• CFrequency
• DWave speed

Which wave property determines the pitch of a sound wave heard by human ears?

• AFrequency
• BAmplitude
• CWave height
• DTrough depth

Why are digital signals generally preferred over analog signals for long-distance communication?

• ADigital signals can be cleaned of noise and digitized as distinct binary values (0s and 1…
• BDigital signals travel faster than the speed of light.
• CAnalog signals cannot carry sound or image data.
• DDigital signals do not require any energy to transmit.

Which pH value indicates a neutral solution at room temperature?

• A7
• B1
• C14
• D0

A student mixes baking soda and vinegar in a beaker sealed with a balloon. The balloon expands as gas forms. Which statement describes this chemical phenomenon?

• AA chemical change occurred, forming carbon dioxide gas while conserving total mass.
• BA physical change occurred because liquid turned into gas without new substances forming.
• CThe total mass increased because gas weighs more than liquid reactants.
• DAtoms were destroyed when the solid dissolved in the liquid.

An atom of Carbon has an atomic number of 6 and a mass number of 14. How many neutrons does this isotope contain?

• A8
• B6
• C14
• D20

When ice melts into liquid water at 0°C, what happens to the arrangement and energy of the water particles?

• AThermal energy is absorbed to overcome rigid crystalline intermolecular bonds, allowing p…
• BThermal energy is released, causing molecules to lock into rigid fixed positions.
• CThe kinetic energy decreases significantly as phase change occurs.
• DWater molecules break down into separate hydrogen and oxygen gas atoms.

Which of the following best represents a balanced chemical equation demonstrating the law of conservation of mass?

• A2H₂ + O₂ → 2H₂O
• BH₂ + O₂ → H₂O
• CCH₄ + O₂ → CO₂ + H₂O
• DNa + Cl₂ → NaCl

A swimmer pushes backward against the water with their hands. According to Newton's third law of motion, what propels the swimmer forward?

• AThe water exerts an equal and opposite force pushing the swimmer forward.
• BThe swimmer's mass decreases as kinetic energy is generated.
• CGravity pulls the swimmer across the surface of the pool.
• DThe swimmer creates a vacuum that pulls their body forward.

Box A has a mass of 10 kg and Box B has a mass of 30 kg. If the same net force of 60 N is applied to both boxes, how do their accelerations compare?

• ABox A accelerates at 6 m/s², which is 3 times faster than Box B (2 m/s²).
• BBox B accelerates 3 times faster than Box A because it has more mass.
• CBoth boxes accelerate at the same rate of 6 m/s².
• DBox A accelerates at 600 m/s² while Box B accelerates at 1800 m/s².

What happens to the frequency of a wave if its wavelength decreases while the wave speed remains constant?

• AThe frequency increases.
• BThe frequency decreases.
• CThe frequency remains unchanged.
• DThe amplitude increases proportionally.

Which phenomenon occurs when light waves pass from air into water and bend due to a change in speed?

• ARefraction
• BReflection
• CAbsorption
• DDiffraction

Two identical metal blocks of equal mass are placed in contact and insulated from their surroundings. Block X is at 90°C and Block Y is at 20°C. What will occur until thermal equilibrium is reached?

• AHeat flows spontaneously from Block X to Block Y until both reach 55°C.
• BCold energy flows from Block Y to Block X until both reach 0°C.
• CHeat flows from Block Y to Block X until Block X reaches 110°C.
• DNo energy transfers because metal blocks do not conduct thermal energy.

Which scenario best illustrates kinetic energy converting into potential energy?

• AA roller coaster car rolling upward to the top of a hill and slowing down.
• BA rock falling freely off a high cliff toward the ground.
• CA car accelerating down a straight highway.
• DA battery lighting up a flashlight bulb.

Why do sound waves require a medium (such as air, water, or steel) to travel, whereas light waves do not?

• ASound is a mechanical wave that propagates via physical particle collisions, while light…
• BSound waves travel faster than light waves and push matter aside.
• CLight waves are mechanical vibrations of air atoms.
• DSound consists of streams of photons that absorb solid matter.

What property of an element is determined by the total number of protons in its atomic nucleus?

• AAtomic number and elemental identity
• BAtomic mass number only
• CIsotope classification
• DState of matter at room temperature

A student pushes a heavy wooden box across a floor at a constant velocity. What can be concluded about the forces acting on the box?

• AThe pushing force is equal in magnitude and opposite in direction to the friction force.
• BThe pushing force is greater than the friction force.
• CThere are no forces acting on the box.
• DGravity is the only force acting on the box.

Which method of heat transfer occurs when warm liquid or gas rises and cooler liquid or gas sinks, creating a circulating current?

• AConvection
• BConduction
• CRadiation
• DInsulation

How does increasing the frequency of a wave affect its energy, assuming amplitude remains constant?

• AThe energy of the wave increases.
• BThe energy of the wave decreases.
• CThe energy of the wave remains completely unchanged.
• DThe energy transforms into mass.

In a closed system containing 50 g of reactant A and 30 g of reactant B, a chemical reaction produces 40 g of solid product C and an unknown mass of gas product D. What is the mass of gas D produced?

• A40 g
• B80 g
• C120 g
• D10 g

Why do metals conduct electricity and thermal energy efficiently compared to nonmetals?

• AMetals contain outer electrons that move freely among positive metal ions in a metallic b…
• BMetals have tightly bound electrons that cannot move.
• CMetals absorb all surrounding light rays.
• DMetal nuclei continuously split into smaller subatomic fragments.

A 1,200 kg car traveling at 20 m/s applies its brakes and stops in 4 seconds. What is the magnitude of the average braking force required?

• A6,000 N
• B24,000 N
• C1,500 N
• D96,000 N

An investigator heats a 100 g sample of unknown liquid X. Graphing thermal energy input versus temperature yields a flat horizontal line at 78°C for 5 minutes despite continuous heating. What scientific conclusion is supported?

• ALiquid X is undergoing a phase change (boiling) at its boiling point of 78°C, during whic…
• BLiquid X has reached thermal absolute zero.
• CThe heating element stopped supplying energy.
• DChemical bonds were created that destroyed thermal energy.

In a fiber optic cable, light signals propagate long distances with minimal loss of intensity. Which physical wave phenomenon makes total internal reflection inside the glass core possible?

• ALight strikes the core-cladding boundary at an angle greater than the critical angle, und…
• BLight waves slow down until they freeze in place.
• CLight is continuously absorbed and re-emitted as sound waves.
• DThe core material transforms transverse light into longitudinal pressure waves.

Which statement correctly describes how neutral sodium (Na, group 1) and chlorine (Cl, group 17) react chemically to form sodium chloride (NaCl)?

• ASodium transfers one valence electron to chlorine, forming Na⁺ and Cl⁻ ions that attract…
• BSodium and chlorine share 4 pairs of neutrons equally.
• CChlorine transfers 7 protons to sodium to balance their nuclei.
• DSodium destroys its nucleus to fuse with chlorine.

A rocket launches off the ground into space. Which statement accurately analyzes the reaction force according to Newton's third law?

• AThe rocket engine exerts a downward force on exhaust gas, and the exhaust gas exerts an e…
• BThe rocket pushes against atmosphere air molecules to lift upward.
• CThe rocket engine creates net energy out of nothing to propel forward.
• DGravity turns off once the rocket ignites its fuel.

A student measures the period of a pendulum swinging back and forth. How would increasing the mass of the pendulum bob affect the period of the pendulum, assuming length and gravity remain constant?

• AThe period remains unchanged because pendulum period depends on string length and gravity…
• BThe period increases significantly because mass slows down the swing.
• CThe period decreases to zero.
• DThe pendulum stops swinging immediately.

Why does a metal spoon sitting in a hot cup of soup feel hot much faster than a wooden spoon sitting in the same soup?

• AMetal has a higher thermal conductivity than wood, allowing heat to transfer rapidly by c…
• BMetal creates thermal energy, while wood destroys heat.
• CWood reflects all heat waves away from the soup.
• DMetal spoons absorb cold from the surrounding air.

Which plant cell organelle is the site of photosynthesis?

• AChloroplast
• BMitochondrion
• CNucleus
• DRibosome

What is the primary function of the cell membrane?

• ATo regulate what enters and leaves the cell
• BTo produce glucose using light energy
• CTo store genetic code in chromosomes
• DTo synthesize digestive enzymes

Which molecules are the primary inputs (reactants) for photosynthesis?

• ACarbon dioxide and water
• BGlucose and oxygen
• CNitrogen and carbon monoxide
• DMethane and hydrogen peroxide

Where does cellular respiration take place in eukaryotic cells to produce ATP energy?

• AMitochondria
• BChloroplasts
• CCell wall
• DVacuole

If a trait is controlled by a dominant allele (B) and a recessive allele (b), what phenotype will an individual with the genotype Bb express?

• AThe dominant phenotype
• BThe recessive phenotype
• CA completely new trait unrelated to B or b
• DNo phenotype

What is a permanent change in the DNA sequence of a gene called?

• AMutation
• BRespiration
• CMitosis
• DAdaptation

According to the theory of natural selection, organisms best adapted to their environment are more likely to:

• ASurvive and reproduce, passing favorable traits to offspring.
• BMutate intentionally whenever danger arises.
• CBecome extinct within one generation.
• DChange their DNA during their lifetime to match surrounding colors.

What type of evidence for evolution is provided by preserved remains or traces of ancient organisms found in rock layers?

• AFossil evidence
• BDNA sequencing
• CEmbryological evidence
• DDirect observation

Which organelle stores water, nutrients, and waste products in plant cells and helps maintain turgor pressure?

• ACentral vacuole
• BRibosome
• CLysosome
• DEndoplasmic reticulum

In a food web, which organisms break down dead organic matter and return nutrients to the soil?

• ADecomposers
• BPrimary producers
• CApex predators
• DHerbivores

What are structures in different species that share a common evolutionary origin and anatomical plan, such as the human arm and a whale flipper, called?

• AHomologous structures
• BAnalogous structures
• CVestigial structures
• DArtificial structures

Two heterozygous tall pea plants (Tt) are crossed. What percentage of the offspring is predicted to be short (tt)?

• A25%
• B50%
• C75%
• D0%