ASVAB General Science Practice Test — with an explanation for every question

The complete free guide to ASVAB General Science

Last reviewed · Written by the Toolskia study team · Independent study material — not affiliated with the U.S. Department of Defense, USMEPCOM, any branch of the armed forces or any official ASVAB program.

General Science is one of the friendliest parts of the ASVAB to prepare for, because it rewards plain familiarity with the science you have met since middle school rather than clever problem-solving or heavy calculation. You are not asked to derive anything or to work long word problems; you are asked whether you know how the body uses oxygen, what an atom is made of, why the seasons change, or which planet is closest to the Sun. That makes General Science a recall game, and recall responds beautifully to short, repeated review. The aim of this guide and the test above is to walk you through every area the subtest covers, hand you the core facts in a way that connects rather than just lists them, and let you drill until the fundamentals are automatic. Work in Practice mode first so every explanation sinks in, then prove your speed under the clock in Mock mode.

Where General Science fits in your ASVAB

Here is the single most important thing to understand about this subtest, and it surprises many test-takers: General Science does not count toward your AFQT. The AFQT — the Armed Forces Qualification Test — is the score that decides whether you can enlist at all, and it is built from only four subtests: Arithmetic Reasoning, Mathematics Knowledge, Word Knowledge and Paragraph Comprehension. General Science is not among them. So a weak General Science score will never stop you from joining; it simply is not part of that gate.

What General Science does do is feed the line scores, also called composite or aptitude-area scores, that each branch uses to decide which jobs you qualify for. General Science is a building block of several of these composites — typically the electronics, mechanical, general technical and skilled-technical lines, with the exact mix varying by service. A specific job lists a minimum line score, so a strong General Science result can be the difference between qualifying for a technical, electronics or medical specialty and just missing the cut. In short: General Science will not get you in the door, but it can open the door to the job you actually want. If you are chasing a science-leaning role, treat it as essential.

The three big areas General Science covers

The subtest spreads its questions across three domains, and knowing the shape of each helps you study efficiently. Life science is usually the largest slice and covers cells and their parts, genetics and heredity, the human body and its systems, nutrition and health, and ecology — food chains, ecosystems and how living things interact. Earth and space science covers the structure of the Earth, the rock cycle, the water cycle, weather and climate, and astronomy: the solar system, the Sun and Moon, and basic facts about the planets. Physical science covers chemistry — atoms, elements, the states of matter, acids and bases — and physics — forces, motion, energy, heat, electricity and simple machines. Because life science carries the most weight, it is the smartest place to start, but a balanced review across all three is what produces a high, reliable score.

Life science: cells, genetics and living things

Begin with the cell, the basic unit of all living things. Know that the nucleus holds the cell's DNA and directs its activity, that the mitochondria are the powerhouses that release energy, that ribosomes build proteins, and that plant cells add a rigid cell wall and green chloroplasts that carry out photosynthesis. Photosynthesis itself is worth memorising as a process: green plants use sunlight, water and carbon dioxide to make sugar and release oxygen, which is the reverse of the respiration animals use to release energy from food. On the genetics side, know that DNA carries hereditary information, that it is packaged into chromosomes, and that genes are the units of inheritance. Round it out with ecology basics — producers, consumers and decomposers in a food chain, and the flow of energy through an ecosystem.

The human body, system by system

Human-body questions are common, so learn the major systems and what each one does. The circulatory system moves blood: the heart pumps it, and red blood cells carry oxygen using the protein hemoglobin. The respiratory system brings in oxygen and removes carbon dioxide, with gas exchange happening in the tiny air sacs of the lungs called alveoli. The digestive system breaks down food for energy, the nervous system — centred on the brain and spinal cord — senses and controls, and the skeletal and muscular systems give structure and movement, meeting at the joints. A handful of memorable numbers help too, such as the adult body having 206 bones, and the skin being the body's largest organ. Knowing which organ does which job — the kidneys filter waste into urine, the liver processes nutrients and toxins, the lungs exchange gases — answers a large share of life-science questions.

Earth and space science

For the Earth, learn its layers from the outside in: the thin solid crust, the thick mantle beneath it, the liquid metal outer core whose motion generates the planet's magnetic field, and the solid inner core at the centre. Know the rock cycle — igneous rock forms from cooled magma or lava, sedimentary rock from compressed layers of sediment, and metamorphic rock from existing rock changed by heat and pressure. The water cycle is a classic: water evaporates, condenses into clouds, falls as precipitation and runs off back to the sea. Add a few atmosphere facts — nitrogen is the most abundant gas in our air at about 78 percent, with oxygen second — and the study of weather, meteorology, and you have the earth-science core. For space, memorise the order of the eight planets from the Sun, that Mercury is closest and Jupiter is the largest, that Saturn is famous for its rings, and that gravity is the force that holds planets in their orbits.

Physical science: chemistry and physics

In chemistry, start with the atom: a central nucleus of positively charged protons and neutral neutrons, orbited by negatively charged electrons. The number of protons is the atomic number and defines which element you have. Know the states of matter and the changes between them — melting, freezing, evaporation (vaporization) and condensation — and the pH scale, where below 7 is acidic, 7 is neutral and above 7 is basic. A few symbols pay off, such as H₂O for water and Au for gold. In physics, learn the difference between speed and velocity (velocity has a direction), that acceleration is the rate at which velocity changes, and the two main kinds of mechanical energy: potential energy is stored by position or height, while kinetic energy is the energy of motion. Know the common SI units — the newton for force, the joule for energy and work, the ampere for electric current — and the three ways heat travels: conduction through direct contact, convection through moving fluids, and radiation through waves.

Handy reference: common units and prefixes

Study strategy that actually works for science recall

Treat science facts the way you would treat vocabulary: review them in short, frequent bursts rather than one exhausting cram, because spaced exposure is what moves information into long-term memory. Start each study block in Practice mode so you read every explanation and connect each fact to a reason — you remember that the outer core is liquid far better when you know it is the moving metal there that makes Earth's magnetic field. Then run a timed Mock to build the quick recall the real subtest rewards. After each run, open the topic breakdown and spend your next ten minutes on your two lowest areas. Bookmark the questions that fool you and use "retry bookmarked" until they no longer do, and keep the daily five-question challenge streak alive for steady exposure.

Common mistakes that cost points

1. Confusing similar terms. Velocity versus speed, potential versus kinetic energy, conduction versus convection — learn the precise difference, because the wrong twin is usually one of the choices. 2. Mixing up the cell organelles. Mitochondria release energy; chloroplasts do photosynthesis; the nucleus holds DNA. Keep their jobs straight. 3. Forgetting that GS is not in the AFQT. Budget your study time by what you need — if you are chasing a technical job, GS earns its hours through the line scores. 4. Leaving a blank. There is no guessing penalty, so always answer. 5. Over-studying one area. Life science is biggest, but ignoring earth or physical science leaves easy points on the table. 6. Memorising without meaning. A fact tied to a reason sticks; a fact memorised cold fades. 7. Cramming the night before. Short daily review beats a single marathon every time. 8. Ignoring units. Knowing the newton, joule and ampere answers a surprising number of physics items outright.

Pro tips for test day

Trust the fundamentals. General Science rewards broad familiarity, so the straightforward, textbook answer is usually right — do not overthink it. Eliminate first. When a question is unfamiliar, cross off the choices you know are wrong; you can often get down to a fifty-fifty. Watch for the close twin. The wrong answer is frequently a term that sounds related, so read all four choices before committing. Never skip. An educated guess can only help. Keep moving. With around 40 seconds per question on the paper version, do not let one item stall you. And after each run on this tool, drill your weakest topic and your bookmarked questions — that is where the next few points are hiding.

Authoritative sources to confirm everything

This guide and tool are for study only, and test details can change. Always confirm specifics with official sources:

• The official ASVAB program (officialasvab.com) — current subtest content, timing, the CAT-ASVAB format and how scores are reported.
• A military recruiter or your local MEPS — the current line-score requirements for the jobs you want, which change over time and differ by branch.
• A reliable science textbook or reference — to confirm any fact and to explore the topics this guide introduces in more depth.

Frequently asked questions

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