General Science: Life, Earth, and Physical Science
Key Takeaways
- General Science is an ASVAB Science/Technical subtest focused on physical and biological science knowledge.
- PiCAT science prep should connect facts to concepts: cells, body systems, ecosystems, rocks, weather, matter, motion, and waves.
- The safest way to answer science items is to identify the field first, then apply the core rule instead of matching a familiar word.
- Scientific-method questions usually test variables, controls, evidence, and conclusions rather than memorized lab vocabulary.
What General Science Covers
Official ASVAB subtest guidance places General Science (GS) in the Science/Technical domain and describes it as knowledge of physical and biological sciences. On PiCAT, the delivery is unproctored and has no individual subtest time limits, but the skill target is still the ASVAB science skill. A verified PiCAT score can become the ASVAB score of record, so science items matter for line-score strength even though GS is not part of AFQT.
GS is broad by design. It can touch life science, earth and space science, chemistry basics, physics, weather, geology, and scientific reasoning. Do not study it as a pile of isolated facts. Build small concept groups, then practice recognizing which group a question belongs to.
On proctored CAT-ASVAB, the official table lists GS as 15 scored questions with a short time limit. PiCAT handles timing differently, but that table is still useful because it shows the intended level: quick recognition of basic science, not long-form problem solving. Prepare to recognize the tested principle, write a tiny note if needed, and move on without outside references.
Scientific Method and Evidence
Science questions often reward process thinking. A hypothesis is a testable explanation. An independent variable is the factor deliberately changed. A dependent variable is the measured result. A control or comparison group helps show whether the tested factor caused the change.
| Term | What it means | PiCAT cue |
|---|---|---|
| Hypothesis | Testable prediction | What should happen if the idea is right |
| Independent variable | Changed factor | Light level, temperature, dosage, material |
| Dependent variable | Measured response | Growth, time, mass, speed, voltage |
| Control | Baseline comparison | Same setup without the tested change |
| Conclusion | Evidence-based answer | Supported by data, not preference |
A good conclusion follows the results even if the results contradict the first guess. If two variables change at once, the experiment cannot clearly identify the cause. That is a common exam trap.
Life Science Core
Life science starts with cells. Cells contain structures that perform jobs: the cell membrane controls movement in and out, the nucleus stores genetic instructions, mitochondria release usable energy, and ribosomes help build proteins. Plant cells also have cell walls and chloroplasts.
Photosynthesis occurs in chloroplasts and uses light energy to build sugar from carbon dioxide and water, releasing oxygen. Cellular respiration releases energy from food molecules. Plants do both, but photosynthesis is the process that stores light energy in chemical form.
Genetics questions often ask about DNA, genes, chromosomes, and cell division. A gene is a segment of DNA that helps determine a trait. Mitosis produces matching body cells for growth and repair. Meiosis produces sex cells with half the chromosome number and creates genetic variation.
Human body systems are another high-yield area. The circulatory system moves blood, oxygen, nutrients, hormones, and waste. The respiratory system exchanges gases in the lungs. The digestive system breaks food into usable nutrients. The nervous system sends fast signals, and the endocrine system uses hormones for slower chemical regulation.
Earth and Space Science
Earth science questions usually test layers, cycles, and processes. The atmosphere is mostly nitrogen, then oxygen, with smaller amounts of other gases. Weather occurs mainly in the troposphere, the lowest atmospheric layer. The water cycle includes evaporation, condensation, precipitation, runoff, infiltration, and collection.
Rocks are grouped by formation. Igneous rocks form when melted rock cools. Sedimentary rocks form from compacted particles or chemical deposits. Metamorphic rocks form when heat and pressure change existing rock without fully melting it.
Space science items may ask about gravity, orbits, phases, tides, and the relationship between Earth, Moon, and Sun. Gravity supplies the inward pull that keeps satellites and planets moving in curved paths. Seasons come mainly from Earth's tilted axis, not from Earth being closer to or farther from the Sun.
Physical Science Core
Physical science connects matter, energy, forces, waves, and heat. Matter has mass and occupies space. Solids hold shape, liquids keep volume but take container shape, gases expand to fill available space, and plasmas are ionized gases.
Temperature measures average particle motion. Heat is energy transferred because of temperature difference. Conduction transfers heat through contact, convection moves heat by fluid motion, and radiation transfers energy by electromagnetic waves.
Waves carry energy. Higher frequency means more cycles per second. For electromagnetic waves in a vacuum, higher frequency means shorter wavelength. Radio waves have long wavelengths and low energy compared with X-rays or gamma rays.
How to Answer GS Items
Use a field-first routine:
- Decide whether the item is biology, earth science, chemistry, physics, or scientific method.
- Name the rule or cycle being tested.
- Reject answers that are true facts but from the wrong field.
- Check whether the wording asks for cause, result, definition, or comparison.
This routine prevents word-matching errors. A question about evaporation is about a phase change at a surface, not any gas process. A question about insulin is about endocrine regulation, not digestion just because food appears in the scenario.
For PiCAT, review science in short mixed sets. The test can move between cells, rocks, atoms, waves, and forces quickly. Your goal is not advanced college science. It is accurate, flexible recall of the basic principles ASVAB uses to measure science aptitude.
A student tests whether different amounts of light affect bean plant height. Each plant gets the same soil, water, container, and temperature. Which factor is the independent variable?