20 General Science (GS) Practice Questions & Answers
Every General Science (GS) practice question from the ASVAB Practice Test, with the correct answer and a short explanation.
Start practice test →1. Which organelle is known as the 'powerhouse of the cell' because it produces most of the cell's usable energy?
- A.Ribosome
- B.Cell membrane
- C.Mitochondrion✓ Answer
- D.Nucleus
Mitochondria carry out cellular respiration, breaking down glucose to produce ATP, the molecule cells use for energy, which is why they are called the powerhouse of the cell.
Source: General Science — cell biology (organelle function)Report a problem with this question
2. Which type of blood cell is primarily responsible for fighting infection?
- A.Plasma cells only
- B.Red blood cells
- C.Platelets
- D.White blood cells✓ Answer
White blood cells (leukocytes) are part of the immune system and defend the body against pathogens, while red blood cells carry oxygen and platelets help blood clot.
Source: General Science — human body systems (immune/circulatory)Report a problem with this question
3. How many chromosomes are found in a normal human body (somatic) cell?
- A.46✓ Answer
- B.23
- C.92
- D.48
A normal human somatic cell has 46 chromosomes arranged in 23 pairs, one of each pair inherited from each parent; sex cells (gametes) have only 23.
Source: General Science — genetics basics (human karyotype)Report a problem with this question
4. Which gas do plants release into the air as a product of photosynthesis?
- A.Carbon dioxide
- B.Hydrogen
- C.Nitrogen
- D.Oxygen✓ Answer
In photosynthesis plants use carbon dioxide and water with light energy to make glucose, and oxygen is released as a byproduct when water molecules are split.
Source: General Science — life science (photosynthesis)Report a problem with this question
5. In a food chain, an organism that makes its own food from sunlight is called a:
- A.Producer✓ Answer
- B.Decomposer
- C.Predator
- D.Consumer
Producers (autotrophs), such as green plants, convert sunlight into food through photosynthesis, forming the base of the food chain that consumers and decomposers depend on.
Source: General Science — ecology (trophic levels)Report a problem with this question
6. Which naturally occurring mineral is the hardest, rating 10 on the Mohs hardness scale?
- A.Gold
- B.Talc
- C.Diamond✓ Answer
- D.Quartz
Diamond, made of tightly bonded carbon atoms in a rigid crystal lattice, is the hardest known natural mineral and defines 10 on the Mohs scale, while talc defines the softest at 1.
Source: General Science — geology (Mohs hardness scale)Report a problem with this question
7. Which instrument is used to measure atmospheric (air) pressure?
- A.Hygrometer
- B.Barometer✓ Answer
- C.Thermometer
- D.Anemometer
A barometer measures atmospheric pressure, and falling pressure often signals approaching stormy weather; a thermometer measures temperature, an anemometer wind speed, and a hygrometer humidity.
Source: General Science — meteorology (weather instruments)Report a problem with this question
8. Which is the largest planet in our solar system?
- A.Jupiter✓ Answer
- B.Neptune
- C.Earth
- D.Saturn
Jupiter is the largest planet, a gas giant whose mass exceeds that of all the other planets combined, making it far bigger than Saturn, the second largest.
Source: General Science — astronomy (solar system planets)Report a problem with this question
9. Which planet is closest to the Sun?
- A.Earth
- B.Mercury✓ Answer
- C.Venus
- D.Mars
Mercury is the innermost planet, orbiting closest to the Sun; Venus is second, Earth third, and Mars fourth in order from the Sun.
Source: General Science — astronomy (planetary order)Report a problem with this question
10. What causes the daily cycle of day and night on Earth?
- A.Earth's orbit around the Sun
- B.The Moon's orbit around Earth
- C.The tilt of Earth's axis
- D.Earth's rotation on its axis✓ Answer
Earth rotates once on its axis about every 24 hours, so the side facing the Sun has day while the opposite side has night; the axial tilt causes seasons, not day and night.
Source: General Science — earth/space science (Earth's rotation)Report a problem with this question
11. Which state of matter has no fixed shape and no fixed volume?
- A.Crystal
- B.Liquid
- C.Solid
- D.Gas✓ Answer
A gas has no fixed shape or volume because its particles move freely and spread to fill any container; a solid keeps both shape and volume, and a liquid keeps volume but takes its container's shape.
Source: General Science — physical science (states of matter)Report a problem with this question
12. Which subatomic particle carries a negative electric charge?
- A.Neutron
- B.Electron✓ Answer
- C.Nucleus
- D.Proton
Electrons carry a negative charge and orbit the nucleus, protons carry a positive charge, and neutrons have no charge; in a neutral atom the number of electrons equals the number of protons.
Source: General Science — physical science (atomic structure)Report a problem with this question
13. The atomic number of an element is equal to the number of what in its atoms?
- A.Total particles in the nucleus
- B.Electrons plus neutrons
- C.Protons✓ Answer
- D.Neutrons
The atomic number equals the number of protons in an atom's nucleus, and it defines which element the atom is; the mass number, by contrast, counts protons plus neutrons.
Source: General Science — physical science (atomic number)Report a problem with this question
14. A solution with a pH below 7 is classified as:
- A.Basic
- B.Acidic✓ Answer
- C.Alkaline
- D.Neutral
On the pH scale a value below 7 indicates an acidic solution with a higher concentration of hydrogen ions, exactly 7 is neutral, and above 7 is basic (alkaline).
Source: General Science — physical science (pH scale)Report a problem with this question
15. What is the chemical formula for water?
- A.CO2
- B.H2O✓ Answer
- C.O2
- D.H2O2
Water is H2O, meaning each molecule contains two hydrogen atoms bonded to one oxygen atom; CO2 is carbon dioxide and H2O2 is hydrogen peroxide.
Source: General Science — chemistry basics (chemical formulas)Report a problem with this question
16. Which of Newton's laws states that an object in motion stays in motion, and an object at rest stays at rest, unless acted on by an outside force?
- A.Law of gravitation
- B.First law (inertia)✓ Answer
- C.Third law (action-reaction)
- D.Second law (F = ma)
Newton's first law, the law of inertia, states that an object's motion does not change unless a net external force acts on it, which is why a moving object keeps moving until friction or another force slows it.
Source: General Science — physics (Newton's first law)Report a problem with this question
17. What is the standard scientific unit used to measure force?
- A.Joule
- B.Watt
- C.Newton✓ Answer
- D.Ampere
Force is measured in newtons (N), defined as the force needed to accelerate one kilogram at one meter per second squared; the joule measures energy and the watt measures power.
Source: General Science — physics (SI unit of force)Report a problem with this question
18. The energy an object has because of its motion is called:
- A.Thermal energy
- B.Kinetic energy✓ Answer
- C.Potential energy
- D.Chemical energy
Kinetic energy is the energy of motion and increases with an object's mass and speed, whereas potential energy is stored energy due to position, such as a raised object's gravitational potential energy.
Source: General Science — physics (forms of energy)Report a problem with this question
19. A screw is a simple machine that is essentially which other simple machine wrapped around a cylinder?
- A.Lever
- B.Pulley
- C.Inclined plane✓ Answer
- D.Wheel and axle
A screw is an inclined plane wrapped around a central cylinder; its spiral thread lets a rotating force convert into a strong linear force, making it easier to hold materials together or lift loads.
Source: General Science — physics (simple machines)Report a problem with this question
20. During a thunderstorm you usually see the lightning before you hear the thunder because:
- A.Light travels faster than sound✓ Answer
- B.Sound travels faster than light
- C.Light is louder than sound
- D.Thunder happens after the lightning ends
Light travels far faster than sound, so the flash of lightning reaches your eyes almost instantly while the thunder, traveling at the much slower speed of sound, arrives noticeably later.
Source: General Science — physics (speed of light vs. sound)Report a problem with this question
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