HiSET Science Practice Test

25 practice questions

Choose an answer, then check it under Show answer.

1. Question 1 of 25Easy

   In cold climates, liquid water frequently seeps into tiny fissures within exposed bedrock, freezes, expands, and eventually fractures the rock into smaller fragments. Which process does this scenario describe?

   1. AA. Glacial deposition
   2. BB. Physical weathering
   3. CC. Chemical weathering
   4. DD. Wind erosion
   Show answer to question 1

   Answer: B. Physical weathering

   Frost wedging is a classic example of physical weathering, which mechanically breaks rocks into smaller pieces without altering their chemical composition. Chemical weathering is incorrect because the mineral structure of the rock is not chemically transformed by the freezing water.

2. Question 2 of 25Easy

   A student wants to test whether adding compost to soil increases radish root mass. Group 1 receives potting soil mixed with compost and is placed on a sunny windowsill. Group 2 receives only potting soil and is placed in a shaded corner of the room. Why is this experimental setup flawed?

   1. AA. Radishes do not require organic matter to grow successfully in indoor settings
   2. BB. Both groups contained the same underlying type of potting soil
   3. CC. The student measured root mass instead of total leaf surface area
   4. DD. Sunlight exposure was not kept constant between the two groups
   Show answer to question 2

   Answer: D. Sunlight exposure was not kept constant between the two groups

   In a controlled experiment, all variables except the one being tested must be kept constant. Because sunlight exposure varied between the two locations, the student cannot determine whether differences in radish root mass were caused by the compost or by light differences. The option noting that both groups had the same potting soil describes proper experimental control rather than a flaw.

3. Question 3 of 25Easy

   An observer on Earth views a full moon. What is the approximate arrangement of the Sun, Earth, and Moon in space at this time?

   1. AA. The Sun is located between Earth and the Moon.
   2. BB. The Moon and the Sun are at a 90-degree angle from Earth.
   3. CC. Earth is located between the Sun and the Moon.
   4. DD. The Moon is located between Earth and the Sun.
   Show answer to question 3

   Answer: C. Earth is located between the Sun and the Moon.

   A full moon occurs when Earth is positioned roughly between the Sun and the Moon, allowing the illuminated half of the Moon to face Earth directly. The arrangement where the Moon is between Earth and the Sun results in a new moon.

4. Question 4 of 25Easy

   An unusually wet spring produces an exceptionally heavy crop of seeds across a desert valley, prompting a large boom in the kangaroo rat population. How will the local population of barn owls, which feed almost entirely on kangaroo rats, most likely respond over the following year?

   1. AA. The owl population will decrease because the dense rodent population disrupts aerial hunting.
   2. BB. The owl population will abandon the valley because excess rodents overgraze the landscape.
   3. CC. The owl population will increase as higher prey abundance supports better survival and reproduction.
   4. DD. The owl population will stay completely constant because apex predators do not track prey cycles.
   Show answer to question 4

   Answer: C. The owl population will increase as higher prey abundance supports better survival and reproduction.

   Predator populations typically increase following a boom in their primary prey because the abundant food supply lowers juvenile starvation and enables higher reproductive success. Predators do not remain constant during sustained prey surges, as availability of food is a major limiting factor regulating carnivore abundance.

5. Question 5 of 25Medium

   Water taken up by plant roots moves through a plant and escapes as vapor through openings in the leaves. What is this part of the water cycle called?

   1. AA. Transpiration
   2. BB. Sublimation
   3. CC. Percolation
   4. DD. Evaporation from soil
   Show answer to question 5

   Answer: A. Transpiration

   Transpiration is the release of water vapor from plant leaves, returning water from the ground to the atmosphere. Evaporation from soil also adds vapor to the air, but it does not involve water passing through a plant.

6. Question 6 of 25Medium

   At a convergent boundary where an oceanic plate meets a continental plate, why does the oceanic plate usually subduct?

   1. AA. Both plates have equal density, so the smaller one sinks.
   2. BB. The oceanic plate is thicker than the continental plate.
   3. CC. The continental plate is denser than the oceanic plate.
   4. DD. The oceanic plate is denser than the continental plate.
   Show answer to question 6

   Answer: D. The oceanic plate is denser than the continental plate.

   Oceanic crust is made of denser rock than continental crust, so it bends and sinks into the mantle at a subduction zone. Thickness does not determine which plate subducts, and continental crust is less dense, not more dense.

7. Question 7 of 25Medium

   How do decomposers such as bacteria and fungi fit into the flow of energy within a food web?

   1. AA. They extract remaining chemical energy from wastes and dead tissue.
   2. BB. They act as primary consumers by feeding only on living plant roots.
   3. CC. They recycle trapped energy back to primary producers for reuse.
   4. DD. They convert solar energy into usable nutrients for the soil.
   Show answer to question 7

   Answer: A. They extract remaining chemical energy from wastes and dead tissue.

   Decomposers obtain energy by breaking down organic molecules contained in dead organisms and cellular wastes. Energy does not cycle indefinitely back into producers because energy flows in one direction and dissipates as heat, even though nutrients themselves are recycled.

8. Question 8 of 25Medium

   A balanced chemical equation represents the reaction between nitrogen gas and hydrogen gas to produce ammonia: N2(g) + 3H2(g) -> 2NH3(g). Based on this equation, what is the ratio of hydrogen molecules consumed to ammonia molecules produced?

   1. AA. 1 to 2
   2. BB. 3 to 1
   3. CC. 2 to 3
   4. DD. 3 to 2
   Show answer to question 8

   Answer: D. 3 to 2

   The coefficients in the balanced equation indicate that 3 molecules of hydrogen gas are required to form 2 molecules of ammonia, giving a ratio of 3 to 2. Comparing the coefficient of nitrogen to ammonia yields a 1 to 2 ratio, which overlooks that the question specifically asks for hydrogen.

9. Question 9 of 25Medium

   A cell builds proteins by joining amino acids in a specific order. Which structure carries out this job?

   1. AA. ribosome
   2. BB. lysosome
   3. CC. Golgi apparatus
   4. DD. vacuole
   Show answer to question 9

   Answer: A. ribosome

   Ribosomes are the structures where amino acids are linked together to form proteins. The Golgi apparatus packages and ships proteins after they are built, but it does not assemble them from amino acids.

10. Question 10 of 25Medium

    A student uses a balance that reads 0.5 g too high every time. She measures the same object five times and averages the readings. What is the effect of averaging on the result?

    1. AA. The average will be exactly correct because five trials are used.
    2. BB. The average will still be about 0.5 g too high.
    3. CC. The average will be too low by an amount that grows with each trial.
    4. DD. The average will have no systematic error because the trials are repeated.
    Show answer to question 10

    Answer: B. The average will still be about 0.5 g too high.

    The balance has a systematic error: every reading is shifted in the same direction by the same amount. Averaging repeated readings reduces random variation but does not cancel a consistent offset, so the average remains about 0.5 g too high. Using five trials does not make the balance correct.

11. Question 11 of 25Easy

    In a laboratory activity, a student places identical effervescent antacid tablets into beakers of water maintained at 10°C, 25°C, 40°C, and 60°C. The student uses a digital timer to measure the exact number of seconds from when each tablet contacts the water until all fizzing stops. What is the dependent variable in this investigation?

    1. AA. Total mass of the antacid tablet
    2. BB. Time required for the fizzing to stop
    3. CC. Initial temperature of the water
    4. DD. Volume of water in each beaker
    Show answer to question 11

    Answer: B. Time required for the fizzing to stop

    The dependent variable is the responding factor measured to gauge the reaction rate, which is the time required for bubbling to cease. The initial water temperature is the independent variable manipulated by the student. Tablet mass and water volume are controlled variables that must remain constant.

12. Question 12 of 25Easy

    How do the nervous and endocrine systems help maintain homeostasis?

    1. AA. Hormones carry electrical signals, while nerves travel in the blood.
    2. BB. Both systems filter wastes from the blood.
    3. CC. Both systems make digestive enzymes for the stomach.
    4. DD. Nerves carry electrical signals, while hormones travel in the blood.
    Show answer to question 12

    Answer: D. Nerves carry electrical signals, while hormones travel in the blood.

    The nervous system uses electrical signals along nerves, and the endocrine system uses hormones carried in blood to coordinate organs. The reversed statement confuses the two systems.

13. Question 13 of 25Easy

    A student places 50 grams of solid ice into an airtight, sealed glass jar that has an empty mass of 150 grams. The combined initial mass of the jar and ice is 200 grams. The jar remains sealed at room temperature until all the ice melts into liquid water. What is the total mass of the jar and its contents after the ice melts?

    1. AA. 195 grams
    2. BB. 205 grams
    3. CC. 200 grams
    4. DD. 150 grams
    Show answer to question 13

    Answer: C. 200 grams

    A phase change from solid ice to liquid water is a physical change that does not alter the number of water molecules present. In an airtight, sealed container, no matter enters or escapes, so the total mass remains exactly 200 grams. The value of 195 grams is incorrect because it relies on the common misconception that water loses mass when transitioning from a solid to a liquid.

14. Question 14 of 25Hard

    In an exposed road cut, a geologist observes four geological features: sedimentary Layer 1 at the bottom, sedimentary Layer 2 directly above it, a fault line that displaces both Layer 1 and Layer 2, and sedimentary Layer 3 that lies undisturbed across the top of the fault line. Which sequence represents the correct chronological order of these events from oldest to youngest?

    1. AA. Deposition of Layer 1, deposition of Layer 2, faulting, deposition of Layer 3
    2. BB. Deposition of Layer 1, faulting, deposition of Layer 2, deposition of Layer 3
    3. CC. Faulting, deposition of Layer 1, deposition of Layer 2, deposition of Layer 3
    4. DD. Deposition of Layer 3, faulting, deposition of Layer 2, deposition of Layer 1
    Show answer to question 14

    Answer: A. Deposition of Layer 1, deposition of Layer 2, faulting, deposition of Layer 3

    By superposition, Layer 1 was deposited before Layer 2. By cross-cutting relationships, the fault must be younger than the layers it cuts (Layer 1 and Layer 2). Because Layer 3 is continuous and unbroken across the fault, the faulting occurred before Layer 3 was deposited. Claiming faulting occurred first is impossible because a fault cannot break rock layers that have not yet formed.

15. Question 15 of 25Hard

    A nuclear power plant generates electricity from nuclear fuel. Which sequence traces the main energy transformations from the fuel to the electrical output?

    1. AA. Nuclear energy to mechanical energy to thermal energy to electrical energy
    2. BB. Nuclear energy to thermal energy to mechanical energy to electrical energy
    3. CC. Thermal energy to nuclear energy to mechanical energy to electrical energy
    4. DD. Nuclear energy to electrical energy to thermal energy to mechanical energy
    Show answer to question 15

    Answer: B. Nuclear energy to thermal energy to mechanical energy to electrical energy

    Fission releases nuclear energy as thermal energy, which makes steam that spins a turbine to produce mechanical energy, and the generator converts that to electrical energy. Placing mechanical energy before thermal energy would mean the turbine spins before heat is released.

16. Question 16 of 25Medium

    A plant cell is placed in a solution that has a higher concentration of dissolved salts than the cell's interior. Which result is most likely?

    1. AA. Nothing changes because plant cell walls stop all movement.
    2. BB. Salt is actively pumped out until both sides match.
    3. CC. Water leaves the cell and the cell shrinks and may wilt.
    4. DD. Water enters the cell and the cell swells and stays firm.
    Show answer to question 16

    Answer: C. Water leaves the cell and the cell shrinks and may wilt.

    The salt solution is hypertonic to the cell, so water diffuses out of the cell, causing it to lose volume and the plant to wilt. Cell walls provide support, but they do not stop water from crossing the membrane.

17. Question 17 of 25Hard

    A biologist discovers a population of beetles living on a windy island where almost all individuals have unusually short wings. To determine whether short wings are an inherited trait or an acquired response to the wind, which experimental procedure would be most effective?

    1. AA. Raise offspring of the island beetles in a windless laboratory to see what wing length develops.
    2. BB. Measure the average wind speed on the island across several different seasons.
    3. CC. Transfer winged beetles from the mainland to observe whether their wings shorten in the wind.
    4. DD. Count the number of short-winged beetles eaten by predatory birds on the island.
    Show answer to question 17

    Answer: A. Raise offspring of the island beetles in a windless laboratory to see what wing length develops.

    Raising offspring in a controlled environment without wind isolates genetic factors from environmental influences, revealing whether the short-wing phenotype appears regardless of external conditions. Simply observing mainland beetles exposed to wind tests short-term physical damage or response, but does not definitively establish the genetic basis of the island population's traits.

18. Question 18 of 25Medium

    Which pair of substances is used up by photosynthesis and released as products of cellular respiration?

    1. AA. Carbon dioxide and water
    2. BB. Glucose and carbon dioxide
    3. CC. Oxygen and water
    4. DD. Glucose and oxygen
    Show answer to question 18

    Answer: A. Carbon dioxide and water

    Photosynthesis takes in carbon dioxide and water to build glucose and release oxygen, while cellular respiration breaks down glucose with oxygen and releases carbon dioxide and water. Glucose and oxygen are the reverse pair: they are the products of photosynthesis and the inputs of respiration. Oxygen and water, and glucose and carbon dioxide, do not match the inputs and outputs of either process.

19. Question 19 of 25Medium

    Over 30 years, a region averaged 25 cm of precipitation per year. Which conclusion is best supported by this information?

    1. AA. Every year in the 30-year period had exactly 25 cm of precipitation.
    2. BB. It will not rain in the region next year.
    3. CC. The region has a relatively dry climate over that long period.
    4. DD. The region's weather never varies from day to day.
    Show answer to question 19

    Answer: C. The region has a relatively dry climate over that long period.

    An average over 30 years describes climate, and 25 cm per year is a relatively small amount of precipitation. The average does not mean every year had exactly that amount, because yearly weather varies around the average. It also cannot predict that no rain will fall next year.

20. Question 20 of 25Medium

    Health guidelines recommend that healthcare workers stay at least six feet away from patients with a specific respiratory infection, claiming the pathogen spreads primarily via large respiratory droplets rather than fine airborne aerosols. Which observation would most strongly challenge this claim and suggest airborne aerosol transmission instead?

    1. AA. The pathogen lost its ability to cause infection after being exposed to ultraviolet light for ten minutes in a laboratory setting.
    2. BB. Susceptible individuals became infected after spending time in a well-ventilated room hours after the infected patient had already departed.
    3. CC. Wearing an ordinary surgical mask over the mouth and nose significantly reduced the rate of infection among bedside nurses.
    4. DD. Household contacts who shared a bed with an infected patient developed symptoms much more frequently than casual acquaintances.
    Show answer to question 20

    Answer: B. Susceptible individuals became infected after spending time in a well-ventilated room hours after the infected patient had already departed.

    Large droplets fall quickly to the ground within a few feet, whereas microscopic aerosols can remain suspended and infectious in the air for hours after the source has left the area. Infection occurring long after an infected person leaves directly contradicts the claim of large-droplet transmission. Higher infection rates among people sharing a bed supports close-contact spread, which is consistent with droplet transmission rather than challenging it.

21. Question 21 of 25Medium

    Two identical spheres carrying negative electric charges are placed near each other in a vacuum chamber. Which statement correctly identifies the directions of the interactions between the spheres?

    1. AA. Both the gravitational force and the electrical force push the spheres apart.
    2. BB. Both the gravitational force and the electrical force pull the spheres together.
    3. CC. Gravitational force pushes the spheres apart, while electrical force pulls them together.
    4. DD. Gravitational force pulls the spheres together, while electrical force pushes them apart.
    Show answer to question 21

    Answer: D. Gravitational force pulls the spheres together, while electrical force pushes them apart.

    Mass always attracts other mass, so the gravitational interaction pulls the two spheres toward one another. Because both spheres carry like negative charges, the electrostatic interaction repels them, pushing them apart. Thinking that both forces pull together overlooks the fundamental rule that like charges repel.

22. Question 22 of 25Hard

    A student attempts to identify an unknown white crystalline powder by performing three simple tests. Test 1 shows the powder dissolves completely in room-temperature water. Test 2 shows the powder does not melt when heated up to 200 degrees Celsius. Test 3 shows that adding drops of vinegar causes vigorous bubbling and gas release. Which of the following correctly pairs an observed property from these tests with its classification?

    1. AA. Resistance to melting is a physical property; dissolving in water is a chemical property.
    2. BB. Resistance to melting is a chemical property; dissolving in water is a physical property.
    3. CC. Dissolving in water is a chemical property; bubbling with vinegar is a physical property.
    4. DD. Bubbling with vinegar is a chemical property; dissolving in water is a physical property.
    Show answer to question 22

    Answer: D. Bubbling with vinegar is a chemical property; dissolving in water is a physical property.

    Bubbling upon the addition of vinegar indicates a chemical reaction that produces a new gas, which demonstrates a chemical property. Dissolving in water does not alter the chemical identity of the substance, meaning solubility is classified as a physical property.

23. Question 23 of 25Hard

    A comet travels along an elongated elliptical orbit around the Sun. As the comet moves from its aphelion (farthest point) toward its perihelion (closest point), how do the gravitational force on the comet and its orbital speed change?

    1. AA. The gravitational force decreases, but the comet speeds up.
    2. BB. The gravitational force decreases, and the comet slows down.
    3. CC. The gravitational force increases, and the comet speeds up.
    4. DD. The gravitational force remains constant, while the comet slows down.
    Show answer to question 23

    Answer: C. The gravitational force increases, and the comet speeds up.

    As the distance between the comet and the Sun decreases, Newton's law of universal gravitation dictates that the gravitational force between them increases. This increasing inward force accelerates the comet along its orbital trajectory, causing it to reach its highest orbital speed at perihelion.

24. Question 24 of 25Hard

    A researcher discovers that a mutation occurring just outside the coding region of a gene alters an inherited trait in fruit flies. The amino acid sequence of the final protein is identical to the normal version, yet the flies exhibit an altered phenotype. Which explanation best accounts for this observation?

    1. AA. The mutation caused the organism to inherit three complete sets of every chromosome.
    2. BB. The mutation changed a regulatory region that controls how much protein is produced.
    3. CC. The mutation converted genomic DNA into transfer RNA directly inside the nucleus.
    4. DD. The mutation destroyed all ribosomal subunits, permanently halting protein synthesis.
    Show answer to question 24

    Answer: B. The mutation changed a regulatory region that controls how much protein is produced.

    DNA contains non-coding regulatory sequences, such as promoters and enhancers, that determine when, where, and how much of a protein is synthesized. A mutation in these regions can dramatically change an organism's traits by altering gene expression levels without changing the protein's primary structure. Destroying all ribosomes would cause widespread cell death rather than a specific, viable phenotype with an otherwise normal protein.

25. Question 25 of 25Hard

    A student generates ripples in a wave tank. When the wave generator oscillates at 4 hertz, the distance between two consecutive wave crests is 6 centimeters. If the generator frequency is adjusted to 12 hertz and wave speed in the tank remains constant, what is the new distance between two consecutive wave crests?

    1. AA. 2 centimeters
    2. BB. 24 centimeters
    3. CC. 3 centimeters
    4. DD. 18 centimeters
    Show answer to question 25

    Answer: A. 2 centimeters

    The initial speed of the water wave is 4 hertz multiplied by 6 centimeters, which equals 24 centimeters per second. When the frequency triples to 12 hertz at constant speed, the wavelength must decrease by a factor of three, giving 24 divided by 12, which equals 2 centimeters. Choosing 18 centimeters results from multiplying the original wavelength by three rather than dividing it.

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