General Science is a broad subtest covering biology, chemistry, physics, earth science, and astronomy at a basic level. It rewards recognition of fundamental facts rather than deep calculation — the kind of science you'd encounter in middle and early high school.
How these questions were selected
These 10 questions were curated by the 247SimpleTests Editorial Team from our General Science practice bank. Each was selected because it covers a concept that appears frequently on the real exam and that many candidates find difficult on their first attempt. The full practice test has 25 questions — work through all of them once you've reviewed this guide.
The questions
Question 1
Which part of the cell is known as the 'powerhouse' because it produces energy (ATP)?
- Nucleus
- Mitochondria ✓
- Ribosome
- Cell membrane
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The MITOCHONDRIA are the 'powerhouse of the cell' — they produce energy in the form of ATP through cellular respiration. ASVAB General Science tests basic biology. Other organelles: NUCLEUS (contains DNA, controls the cell); RIBOSOMES (make proteins); CELL MEMBRANE (controls what enters/exits); CHLOROPLASTS (in plant cells, do photosynthesis). The mitochondria-as-powerhouse fact is one of the most commonly tested cell biology points.
Source: ASVAB General Science — Cell BiologyQuestion 2
What is the chemical symbol for water?
- CO2
- H2O ✓
- O2
- NaCl
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WATER is H2O — two hydrogen atoms bonded to one oxygen atom. ASVAB General Science includes basic chemistry. Other common formulas: CO2 (carbon dioxide); O2 (oxygen gas); NaCl (sodium chloride/table salt); CH4 (methane). Knowing common chemical formulas and symbols (H = hydrogen, O = oxygen, C = carbon, Na = sodium) is frequently tested. Water (H2O) is the most basic and essential formula to know.
Source: ASVAB General Science — Chemistry BasicsQuestion 4
On the pH scale, a substance with a pH of 7 is considered:
- Acidic
- Neutral ✓
- Basic (alkaline)
- Radioactive
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A pH of 7 is NEUTRAL (neither acidic nor basic) — pure water is neutral. ASVAB General Science includes the pH scale. The scale runs 0-14: BELOW 7 = ACIDIC (lower = more acidic, e.g., lemon juice, stomach acid); ABOVE 7 = BASIC/ALKALINE (higher = more basic, e.g., bleach, soap); EXACTLY 7 = NEUTRAL. Knowing that 7 is neutral, below 7 is acidic, and above 7 is basic is a commonly tested chemistry concept.
Source: ASVAB General Science — Chemistry, pH ScaleQuestion 5
Which planet is closest to the Sun?
- Venus
- Mercury ✓
- Earth
- Mars
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MERCURY is the planet closest to the Sun. ASVAB General Science includes astronomy. The planets in order from the Sun: MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, URANUS, NEPTUNE (a common mnemonic: 'My Very Educated Mother Just Served Us Noodles'). Mercury is closest (and has extreme temperatures); Venus is hottest (due to its thick atmosphere/greenhouse effect); Jupiter is largest. Knowing planetary order, especially Mercury as closest, is commonly tested.
Source: ASVAB General Science — Astronomy, PlanetsQuestion 6
What process do plants use to convert sunlight, water, and carbon dioxide into food (glucose) and oxygen?
- Respiration
- Photosynthesis ✓
- Digestion
- Fermentation
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PHOTOSYNTHESIS is the process by which plants (using chlorophyll in chloroplasts) convert SUNLIGHT, WATER, and CARBON DIOXIDE into GLUCOSE (food/energy) and release OXYGEN. ASVAB General Science covers this key biological process. Equation concept: CO2 + H2O + light energy → glucose + O2. Photosynthesis is the basis of most food chains and produces the oxygen we breathe. CELLULAR RESPIRATION is roughly the reverse (using glucose and oxygen to release energy). Photosynthesis is one of the most commonly tested biology topics.
Source: ASVAB General Science — PhotosynthesisQuestion 7
What gas do humans need to breathe in to survive, and what gas do they exhale?
- Inhale carbon dioxide, exhale oxygen
- Inhale oxygen, exhale carbon dioxide ✓
- Inhale nitrogen, exhale helium
- Inhale hydrogen, exhale oxygen
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Humans INHALE OXYGEN (needed for cellular respiration to produce energy) and EXHALE CARBON DIOXIDE (a waste product of respiration). ASVAB General Science covers the respiratory system. In the lungs, oxygen from inhaled air passes into the blood, and carbon dioxide passes out of the blood to be exhaled (gas exchange in the alveoli). This is essentially the opposite of plant photosynthesis (which uses CO2 and releases O2). The oxygen-in, carbon-dioxide-out cycle is fundamental, commonly tested biology.
Source: ASVAB General Science — Respiratory SystemQuestion 8
Sound travels fastest through which medium?
- A vacuum
- A solid ✓
- A gas
- Sound travels at the same speed everywhere
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Sound travels FASTEST through SOLIDS (then liquids, then gases — slowest in gases like air). ASVAB General Science/physics covers wave properties. Sound is a mechanical wave requiring a medium; it travels faster when particles are closer together (denser, more tightly bound), so: SOLID > LIQUID > GAS. Sound CANNOT travel through a VACUUM (no particles to transmit it — which is why space is silent). The fact that sound travels fastest in solids and not at all in a vacuum is commonly tested.
Source: ASVAB General Science — Physics, SoundQuestion 9
What is the basic unit of electrical resistance?
- Volt
- Ohm ✓
- Ampere
- Watt
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The OHM is the basic unit of electrical RESISTANCE. ASVAB General Science covers basic physics/electricity. Key electrical units: VOLT (voltage/electrical potential); AMPERE/amp (current); OHM (resistance); WATT (power). OHM'S LAW relates them: V = I × R (Voltage = Current × Resistance). Knowing which unit measures which quantity (ohm = resistance) is commonly tested on both General Science and Electronics Information.
Source: ASVAB General Science — ElectricityQuestion 10
What is the innermost layer of the Earth called?
- Crust
- Core ✓
- Mantle
- Atmosphere
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The CORE is the innermost layer of the Earth. ASVAB General Science includes earth science. Earth's layers from outside in: CRUST (thin outer layer where we live); MANTLE (thick middle layer of hot, semi-solid rock); CORE (innermost — divided into a liquid OUTER CORE and a solid INNER CORE, composed mostly of iron and nickel, extremely hot). The Earth's core generates the magnetic field. Knowing Earth's layered structure (crust, mantle, core) is commonly tested earth science.
Source: ASVAB General Science — Earth's LayersGeneral Science essentials: Biology — mitochondria are the cell's powerhouse, skin is the largest organ, photosynthesis makes food from sunlight, white blood cells fight infection. Chemistry — water is H2O, pH 7 is neutral, the three states are solid/liquid/gas. Physics — gravity pulls objects toward Earth, sound travels fastest through solids, the ohm measures resistance. Earth/space — Mercury is closest to the Sun, the Moon causes tides, the core is Earth's innermost layer. Broad recognition beats deep memorization here.
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