Praxis General Science common mistakes
Praxis General Science · Understand the traps and how to avoid them.
Given a short description of an experiment, labels the variable the researcher manipulates as the 'dependent' variable, and calls the untreated comparison group the 'experimental group.'
The terms are memorized as a paired list rather than as a causal story; 'dependent' intuitively sounds like 'the thing you decided to change,' so the labels get swapped even when the underlying logic is understood.
What to do instead
Before answering, rewrite the hypothesis as an if–then sentence: the 'if' clause is the independent variable, the 'then' clause is the dependent variable. The group receiving no treatment is the control; the treated group is experimental. Drill five short scenarios until the mapping is automatic.
Calls a set of measurements that are tightly clustered but far from the accepted value 'accurate,' and doubts data that are widely scattered yet centered on the true value.
Everyday speech uses 'accurate' and 'precise' as loose synonyms for 'good,' so the bull's-eye distinction is never actually practiced against numbers.
What to do instead
Sketch a target diagram on scratch paper: accuracy is how close the center of the cluster sits to the bull's-eye; precision is how tight the cluster is. Then evaluate the actual numbers given rather than the word that sounds more flattering.
Selects 'a theory becomes a law once enough evidence accumulates' or 'a hypothesis that has been proven becomes a theory.'
The casual meaning of 'theory' (a guess) plus the school-lab sequence of hypothesis to conclusion implies a ladder from guess to fact, and no instruction ever explicitly contradicts it.
What to do instead
Memorize the real relationship: theories explain why (mechanisms), laws describe what (regularities); neither is promoted into the other, and both remain open to revision. Treat any answer choice containing 'proven' or 'promoted' as a distractor.
Substitutes Celsius temperatures directly into gas-law relationships or into q = mcΔT, skipping the conversion to kelvin.
Everyday contexts default to Celsius and the conversion feels like a cosmetic extra step, especially under time pressure when the numbers 'look like they will work.'
What to do instead
Write 'T(K) = T(°C) + 273' at the top of the scratch sheet before starting the physical science section and convert every temperature in the problem statement first. Sanity check: a negative volume, negative pressure, or wildly wrong ratio almost always means a Celsius slip.
For an ion such as S²⁻ or Fe³⁺, reports the electron count as equal to the atomic number, or computes neutrons by using the atomic number instead of the mass number.
The neutral-atom shortcut (protons = electrons) is learned first and heavily practiced, so it is never overwritten by the charge rule; similarly the atomic number is the most familiar number on the symbol.
What to do instead
Use a fixed three-line template for every particle: protons = Z; neutrons = A − Z; electrons = Z − (charge). Write it out for at least six species including one cation, one anion, and one isotope before choosing an answer.
Asserts that an object with zero net force must be at rest, and states that Newton's third-law action–reaction pairs cancel each other out.
Pushing furniture around creates a strong intuition that balanced forces mean no motion, and two equal opposite forces naturally look like they should subtract to zero.
What to do instead
Restate both rules until they are reflexive: zero net force means zero acceleration, which includes constant nonzero velocity (an object sliding at steady speed has zero net force). Third-law pairs act on two different objects, so they can never cancel; for every force statement, ask 'on which object does this force act?'
Describes meiosis as producing two genetically identical diploid cells, or places crossing over in mitosis.
Mitosis is taught first and revisited most often, so its product becomes the default answer whenever cell division is mentioned, and the visual of chromosomes lining up looks the same in both diagrams.
What to do instead
Build a two-column mitosis/meiosis table with rows for purpose, number of divisions, number of products, ploidy of products, crossing over, and location in humans, and fill it from memory weekly. Key anchors: meiosis has two divisions, four nonidentical haploid products, and crossing over in prophase I.
Explains antibiotic resistance or any population change with goal-directed language: the bacteria 'adapted in order to survive,' 'learned,' or 'developed resistance when they needed it.'
Everyday speech about adaptation is teleological and Lamarckian phrasing is culturally pervasive, so it slides into written answers even when the correct model is known.
What to do instead
Force every explanation through a four-step template: (1) variation already exists in the population; (2) the environment selects among variants; (3) survivors leave more offspring; (4) allele frequencies shift across generations. Ban the words 'need,' 'try,' and 'in order to' from your written responses.
Attributes summer to Earth being closer to the Sun, and explains monthly moon phases as Earth's shadow falling on the Moon.
The standard elliptical-orbit diagram and the standard eclipse diagram look like they explain the two most familiar sky phenomena, and both are visually almost identical to the correct diagrams.
What to do instead
Anchor the disproofs: Earth is actually nearest the Sun in early January, during Northern Hemisphere winter, so distance cannot drive seasons - the ~23.5° axial tilt changes sunlight angle and day length. Earth's shadow reaches the Moon only at a lunar eclipse, which requires alignment and occurs a few times a year, not monthly; phases come from the changing Sun–Moon–Earth angle.
States that continental crust subducts beneath oceanic crust, and mixes up which landforms form at divergent versus convergent boundaries.
The names suggest that continents, being the large 'plates' of common speech, are the heavy slabs that sink; boundary types are memorized as disconnected lists rather than as directions of relative motion.
What to do instead
Fix the density fact first: oceanic crust (basalt, ~3.0 g/cm³) is denser than continental crust (granite, ~2.7 g/cm³), so oceanic lithosphere always subducts. Then pair each boundary with its motion and products: divergent = ridges, rifting, new crust; ocean–continent convergent = trench, volcanic arc, mountains; transform = strike-slip faulting.