PSSA Science — Grade 8

Which statement correctly describes the location and electrical charge of subatomic particles within an atom?

• AProtons are negatively charged in the nucleus, while electrons are positively charged in…
• BProtons are positively charged and neutrons are neutral in the nucleus, while electrons a…
• CNeutrons are positively charged in the nucleus, while protons and electrons are neutral i…
• DElectrons and protons are both inside the nucleus with neutral charges, while neutrons or…

The atomic number of an element on the periodic table represents which of the following?

• AThe total number of protons in the nucleus of an atom
• BThe combined total number of protons and neutrons
• CThe total number of neutrons minus the number of electrons
• DThe average atomic mass of all naturally occurring isotopes

An atom of Carbon has an atomic number of 6 and contains 7 neutrons in its nucleus. What is the mass number of this Carbon isotope?

• A6
• B7
• C13
• D42

Why are elements in Group 18 of the periodic table (the noble gases like Neon and Argon) extremely unreactive under normal conditions?

• AThey have only one valence electron that is easily lost.
• BTheir outermost energy levels are completely full with 8 valence electrons.
• CThey contain no protons in their nucleus.
• DThey are all metallic solids that resist chemical changes.

When a sodium atom (Na) reacts with a chlorine atom (Cl) to form table salt (NaCl), which process takes place?

• ASodium and chlorine share a pair of electrons equally to form a covalent bond.
• BSodium gains an electron to become a negative ion, while chlorine loses an electron.
• CProtons are transferred from the chlorine nucleus into the sodium nucleus.
• DSodium transfers its one valence electron to chlorine, forming positive (Na+) and negativ…

Which of the following describes a physical change rather than a chemical change?

• AIce melting into liquid water on a warm countertop
• BAn iron nail rusting after exposure to rain and air
• CA piece of wood burning in a fireplace to form ash and smoke
• DBaking soda reacting with vinegar to produce gas bubbles

A student mixes two clear liquid solutions together in a beaker. Which observation provides the BEST evidence that a chemical reaction has occurred?

• AThe total volume of liquid in the beaker increases.
• BThe liquid mixture takes the shape of the beaker.
• CA bright yellow solid precipitate forms and the beaker feels warm.
• DThe liquid can be separated back into two layers by sitting undisturbed.

A student seals 50 grams of vinegar and 10 grams of baking soda inside an airtight plastic container and measures a total initial mass of 120 grams (including the container). After the chemical reaction stops bubbling, what will be the total mass of the sealed container and its contents?

• A60 grams
• B120 grams
• C110 grams
• D130 grams

Consider the chemical equation for water synthesis: 2 H2 + O2 -> 2 H2O. How many total hydrogen atoms and oxygen atoms are present on the reactant side?

• A4 hydrogen atoms and 2 oxygen atoms
• B2 hydrogen atoms and 2 oxygen atoms
• C4 hydrogen atoms and 4 oxygen atoms
• D2 hydrogen atoms and 1 oxygen atom

Dry ice (solid carbon dioxide) transforms directly into carbon dioxide gas at room temperature without turning into a liquid first. What is this phase change called?

• AEvaporation
• BCondensation
• CFreezing
• DSublimation

A student standing on a moving bus lurches forward when the driver suddenly hits the brakes. Which of Newton's laws of motion explains this behavior?

• ANewton's Law of Universal Gravitation
• BNewton's First Law of Motion (Law of Inertia)
• CNewton's Second Law of Motion (F = ma)
• DNewton's Third Law of Motion (Action-Reaction)

A net force of 10 Newtons is applied to a toy car with a mass of 2 kilograms. According to Newton's Second Law (F = ma), what is the acceleration of the toy car?

• A0.2 m/s²
• B5 m/s²
• C12 m/s²
• D20 m/s²

Two students push two grocery carts with the exact same pushing force. Cart A has a mass of 10 kg, and Cart B has a mass of 30 kg. How will their accelerations compare?

• ACart A will accelerate 3 times faster than Cart B because it has less mass.
• BCart B will accelerate 3 times faster than Cart A because it has more mass.
• CBoth carts will accelerate at the exact same rate because the pushing forces are equal.
• DNeither cart will accelerate because mass cancels out force.

A space rocket launches by burning fuel and blasting hot exhaust gas downward out of its engine nozzles. What propels the rocket upward into space?

• AThe exhaust gas pushing against the solid ground below the launchpad
• BThe air atmosphere pushing against the top nose cone of the rocket
• CThe elimination of gravity once the fuel burns
• DThe reaction force of the exhaust gas pushing back upward on the rocket engine

A bicyclist travels a distance of 60 meters in 12 seconds along a straight bike path. What is the average speed of the bicyclist?

• A0.2 m/s
• B5 m/s
• C48 m/s
• D720 m/s

On a distance-versus-time graph, what does a flat, horizontal straight line indicate about an object's motion?

• AThe object is stopped (at rest).
• BThe object is moving at a constant high speed.
• CThe object is accelerating at a steady rate.
• DThe object is returning back to its starting point.

At which point during a roller coaster ride does a coaster car have the MAXIMUM gravitational potential energy?

• AAt the lowest point of the track near the bottom of the first drop
• BHalfway down the main hill while moving at top speed
• CAt the highest point of the highest hill before descending
• DAt the very end of the track after coming to a complete stop

As a pendulum swings downward from its highest release point toward the lowest center point of its arc, what energy conversion takes place?

• AKinetic energy is converted into gravitational potential energy.
• BGravitational potential energy is converted into kinetic energy.
• CChemical energy is converted into electrical energy.
• DThermal energy is converted into nuclear energy.

The formula for kinetic energy is KE = 1/2 m v². If a driver doubles the velocity (v) of a car from 20 mph to 40 mph while keeping mass constant, how does the kinetic energy of the car change?

• AThe kinetic energy remains the same.
• BThe kinetic energy doubles (increases by 2 times).
• CThe kinetic energy triples (increases by 3 times).
• DThe kinetic energy quadruples (increases by 4 times).

A metal spoon gets hot when left inside a bowl of hot soup. Which mode of heat transfer is primarily responsible for heating the spoon handle?

• AConduction
• BConvection
• CRadiation
• DInsulation

In a transverse wave diagram, what is the distance from the crest of one wave to the crest of the next adjacent wave called?

• AAmplitude
• BWavelength
• CTrough
• DFrequency

Wave speed is equal to frequency multiplied by wavelength (v = f λ). If a wave generator increases the frequency of waves traveling at a constant speed in a water tank, what happens to the wavelength of the waves?

• AThe wavelength increases.
• BThe wavelength stays the same.
• CThe wavelength decreases.
• DThe wavelength drops to zero instantly.

A student places a straight pencil into a clear glass cup filled with water and notices that the pencil looks broken or bent at the water's surface. What wave phenomenon causes this optical illusion?

• ARefraction of light as it changes speed passing from air into water
• BReflection of light bouncing off the smooth glass surface
• CAbsorption of light rays by water molecules
• DDiffraction of light spreading around the edges of the pencil

Which statement correctly compares ultraviolet (UV) light waves to radio waves on the electromagnetic spectrum?

• AUV waves have lower frequency and lower energy than radio waves.
• BUV waves have longer wavelengths and higher energy than radio waves.
• CRadio waves have higher frequency and shorter wavelengths than UV waves.
• DUV waves have higher frequency, shorter wavelengths, and higher energy than radio waves.

Why can sunlight travel across outer space to reach Earth, whereas sound from an exploding star cannot be heard across outer space?

• ASound waves travel too fast to be detected by human ears.
• BLight is an electromagnetic wave that requires no medium, while sound is a mechanical wav…
• COuter space is too cold for sound waves to move.
• DSunlight absorbs sound waves before they can leave the star's surface.

A student measures an unknown rock sample and finds its mass is 50 grams and its volume is 20 cubic centimeters (cm³). What is the density of the rock?

• A2.5 g/cm³
• B0.4 g/cm³
• C30 g/cm³
• D1000 g/cm³

What happens when the North pole of one bar magnet is brought close to the South pole of another bar magnet?

• AThe two magnetic poles repel each other.
• BThe magnetic fields cancel out and lose all magnetism.
• CThe two magnetic poles attract each other.
• DAn electric spark is continuously produced between the poles.

A string of holiday lights is wired in a series circuit. If one bulb burns out and breaks its filament, what will happen to the remaining bulbs on the string?

• AAll remaining bulbs will get brighter.
• BAll remaining bulbs will turn off because the electric circuit path is broken.
• COnly the adjacent bulb will turn off.
• DThe remaining bulbs will stay lit because each bulb has its own separate path.

A student wants to dissolve a sugar cube in a glass of water as quickly as possible. Which combination of actions will INCREASE the dissolving rate the most?

• ACooling the water, keeping the sugar cube whole, and letting it sit still
• BCooling the water, crushing the sugar cube, and letting it sit still
• CHeating the water, keeping the sugar cube whole, and stirring slowly
• DHeating the water, crushing the sugar cube into fine powder, and stirring rapidly

Three household liquids are tested with pH paper: Lemon juice has a pH of 2, pure water has a pH of 7, and bleach has a pH of 12. How should these substances be classified?

• ALemon juice is acidic, pure water is neutral, and bleach is basic.
• BLemon juice is basic, pure water is neutral, and bleach is acidic.
• CLemon juice is neutral, pure water is acidic, and bleach is basic.
• DAll three substances are acidic.

Which organelle serves as the control center of a eukaryotic cell by housing its genetic material (DNA)?

• ANucleus
• BRibosome
• CVacuole
• DCell Wall

Why are mitochondria often referred to as the 'powerhouses' of animal and plant cells?

• AThey store large quantities of surplus water for the cell.
• BThey convert glucose and oxygen into usable cellular energy (ATP) through cellular respir…
• CThey absorb sunlight to carry out photosynthesis.
• DThey package proteins into transport vesicles.

A student looks through a light microscope at an unknown cell sample and observes a rigid cell wall and green chloroplasts. What type of cell is the student observing?

• AAnimal cell
• BHuman red blood cell
• CPlant cell
• DFungal cell

Which process describes the passive movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration?

• AActive transport
• BEndocytosis
• CPhagocytosis
• DOsmosis

Nerve cells maintain a higher concentration of potassium ions inside the cell than in the surrounding fluid. What process do nerve cells use to pump potassium ions INTO the cell against their concentration gradient?

• ASimple diffusion
• BActive transport using ATP energy
• COsmosis
• DFacilitated passive diffusion

What are the primary REACTANTS required for plants to carry out photosynthesis?

• ACarbon dioxide, water, and sunlight energy
• BGlucose and oxygen
• COxygen, water, and ATP
• DNitrogen, soil minerals, and carbon dioxide

How are the chemical processes of photosynthesis and cellular respiration related to one another in the global carbon cycle?

• ABoth processes take in carbon dioxide and produce glucose.
• BBoth processes take in oxygen and produce water.
• CThe products of photosynthesis (glucose and oxygen) serve as the starting reactants for c…
• DPhotosynthesis occurs only in animals, while cellular respiration occurs only in plants.

Why do plant leaves typically appear green to human eyes?

• AChlorophyll absorbs green light and uses it to fuel photosynthesis.
• BChlorophyll absorbs ultraviolet light and converts it into green light.
• CChlorophyll absorbs red and blue light wavelengths while reflecting green light wavelengt…
• DPlant cell walls are made of green cellulose crystals.

What is the primary function of mitosis in a multicellular organism like a human?

• ATo create sperm and egg cells for reproduction
• BTo produce two genetically identical daughter cells for body growth and tissue repair
• CTo reduce the chromosome number by half
• DTo combine genetic material from two parents

If a body cell of a frog contains 26 chromosomes, how many chromosomes will be present in a frog egg cell produced by meiosis?

• A13 chromosomes
• B26 chromosomes
• C52 chromosomes
• D104 chromosomes

In the double-helix structure of DNA, which nitrogenous base always pairs with Cytosine (C)?

• AAdenine (A)
• BThymine (T)
• CGuanine (G)
• DUracil (U)

Which pathway correctly describes how genetic information flows within a cell to express traits?

• AProtein -> RNA -> DNA
• BDNA -> RNA -> Protein
• CRNA -> Protein -> DNA
• DCell Wall -> Nucleus -> Ribosome

In pea plants, tall height (T) is dominant over short height (t). What is the term for a plant's physical appearance (such as being 'tall' or 'short')?

• APhenotype
• BGenotype
• CKaryotype
• DChromosome

Two heterozygous pea plants (Bb x Bb) with brown seeds are crossed. Brown (B) is dominant over white (b). What percentage of their offspring is expected to have white seeds?

• A0%
• B25%
• C50%
• D75%

A dog breeder crosses a heterozygous black dog (Bb) with a homozygous recessive white dog (bb). What is the expected ratio of black puppies to white puppies?

• A100% black, 0% white
• B50% black, 50% white
• C75% black, 25% white
• D0% black, 100% white

In snapdragon flowers, crossing a purebred red flower (RR) with a purebred white flower (WW) produces 100% pink flowers (RW). What pattern of inheritance does this demonstrate?

• AComplete Mendelian dominance
• BSex-linked recessive inheritance
• CIncomplete dominance
• DEnvironmental mutation