HESI A2 cheat sheet

Main idea = the central point the entire passage supports; a supporting detail only reinforces it and never covers the whole passage.

Inference = a conclusion logically implied by the text but never stated directly; it must be traceable to specific details or word choices.

Tone is the author's attitude toward the subject; mood is the feeling the text creates in the reader - do not interchange the two.

Chronological structure is signaled by first, next, then, before, finally; cause-effect structure is signaled by because, therefore, as a result.

Compare/contrast is signaled by similarly, unlike, in contrast, both, whereas; problem-solution is signaled by issue, remedy, resolve.

Context clue types: definition (is/means), example (such as), contrast (however/but), restatement (in other words).

Fact statements are verifiable; opinion statements carry judgment words such as should, best, beautiful, ought, too much.

Author's purpose is inform, persuade, entertain, or explain - identify it by what the passage actually does, not by its topic.

A correct summary omits minor details and personal opinions and preserves the main idea plus key supporting points.

Prefixes: pre- before, post- after, anti- against, sub- under, hyper- over/above, hypo- under/below, bi- two, mono- one.

Suffixes: -itis inflammation, -ectomy surgical removal, -ology study of, -algia pain, -emia blood condition, -cyte cell.

Roots: cardi- heart, nephr- kidney, hepat- liver, derm- skin, oste- bone, neur- nerve, pulmon- lung, gastr- stomach.

Color and quantity roots: leuko- white, erythro- red, cyano- blue, brady- slow, tachy- fast, poly- many.

Homophones: their (possessive), there (place), they're (they are); to (direction), too (also), two (number).

Affect is normally a verb meaning to influence; effect is normally a noun meaning the result.

Analogy strategy: state the exact relationship (part-to-whole, function, cause-effect, degree), then apply the same relationship to the answer pair.

Common general knowledge anchors: 206 bones in the adult skeleton, 7 continents, 5 oceans, 60 minutes in an hour, 2.54 cm in an inch.

Subject-verb agreement: a singular subject takes a singular verb; ignore prepositional phrases between subject and verb (The box of tools is heavy).

Two independent clauses may be joined by a comma plus a coordinating conjunction (for, and, nor, but, or, yet, so), by a semicolon, or by a period.

A comma splice joins two independent clauses with only a comma and is an error; replace the comma with a period or semicolon.

A colon must follow an independent clause and introduces a list, explanation, or quotation.

Apostrophes: 's = singular possessive; s' = plural possessive ending in s; its = possessive, it's = it is.

Pronouns must agree with their antecedents in number and person (Each student must bring his or her book).

Active voice = subject performs the action; passive voice = subject receives the action (was given, were tested).

An introductory modifier must describe the subject of the main clause; otherwise it dangles (Walking home, I saw the storm - not Walking home, the storm began).

Use who for subjects and whom for objects; use fewer for countable nouns and less for uncountable nouns.

Order of operations: parentheses, exponents, multiplication/division left to right, addition/subtraction left to right.

To add or subtract fractions, find a common denominator; to divide, multiply by the reciprocal (a/b ÷ c/d = a/b × d/c).

Percent problems: part = percent × whole; percent change = (new − old) ÷ old × 100.

Proportions solve by cross-multiplication: a/b = c/d means ad = bc.

Metric conversions: 1 kg = 1000 g, 1 g = 1000 mg, 1 L = 1000 mL, 1 m = 100 cm, 1 km = 1000 m.

Common equivalents: 1 inch = 2.54 cm, 1 pound = 16 ounces, 1 cup = 8 ounces, 1 hour = 60 minutes.

Area formulas: rectangle lw, triangle ½bh, circle πr²; circumference = 2πr; volume of a rectangular solid = lwh.

Mean = sum ÷ count; median = middle value after ordering; mode = most frequent value.

Roman numerals: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000; a smaller numeral before a larger one is subtracted (IV = 4).

Cell theory: all living things are composed of cells, and all cells arise from pre-existing cells.

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells have a nucleus and membrane-bound organelles.

Mitosis yields two identical diploid cells for growth and repair; meiosis yields four genetically varied haploid gametes.

DNA base pairing: adenine–thymine and guanine–cytosine; RNA substitutes uracil for thymine and pairs A with U.

Photosynthesis: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂, occurring in chloroplasts.

Cellular respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP, occurring mainly in mitochondria.

Organelles: mitochondria produce ATP, ribosomes synthesize protein, lysosomes digest waste, rough ER transports protein.

Osmosis moves water across a semipermeable membrane from low solute concentration to high solute concentration.

Classification order: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Atomic number = number of protons; mass number = protons + neutrons; in a neutral atom, protons equal electrons.

Ionic bonds transfer electrons between a metal and a nonmetal; covalent bonds share electrons, usually between nonmetals.

pH below 7 is acidic, 7 is neutral, above 7 is basic; each whole pH unit is a tenfold change in hydrogen ion concentration.

One mole = 6.022 × 10²³ particles; molar mass is expressed in grams per mole and read from the periodic table.

Molarity = moles of solute ÷ liters of solution; moles = mass ÷ molar mass.

A balanced equation has equal numbers of each atom on both sides, reflecting conservation of mass.

Noble gases have complete valence shells, so they are chemically unreactive; atoms gain, lose, or share electrons to reach a full outer shell.

Acids donate H⁺ ions; bases accept H⁺ ions or release OH⁻ ions; acid + base → salt + water (neutralization).

Exothermic reactions release heat (ΔH negative); endothermic reactions absorb heat (ΔH positive); density = mass ÷ volume.

The adult skeleton has 206 bones: 80 axial (skull, spine, rib cage) and 126 appendicular (limbs and girdles).

The heart has four chambers; the right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the body.

Blood flow: right atrium → right ventricle → pulmonary artery → lungs → left atrium → left ventricle → aorta → body.

Gas exchange occurs in the alveoli; the diaphragm contracts and flattens during inhalation, lowering thoracic pressure.

The nephron is the functional unit of the kidney; filtration occurs in the glomerulus and reabsorption in the tubules.

Most nutrient absorption occurs in the small intestine, where villi and microvilli increase surface area.

The CNS is the brain and spinal cord; the PNS is cranial and spinal nerves, divided into sensory and motor divisions.

Blood components: plasma transports, red blood cells carry oxygen via hemoglobin, white blood cells fight infection, platelets clot.

Insulin from the pancreas lowers blood glucose; glucagon raises it; skeletal muscle is voluntary and striated, cardiac and smooth muscle are involuntary.

Newton's first law: an object at rest or in uniform motion stays that way unless a net force acts (inertia).

Newton's second law: F = ma; Newton's third law: every action has an equal and opposite reaction.

Speed = distance ÷ time; acceleration = change in velocity ÷ time; velocity includes direction, speed does not.

Work = force × distance; power = work ÷ time and is measured in watts; energy is measured in joules.

Kinetic energy = ½mv²; gravitational potential energy = mgh; total energy is conserved in a closed system.

Ohm's law: V = IR; electric power P = IV; resistors in series add directly.

Waves: speed = frequency × wavelength (v = fλ); frequency is measured in hertz.

Pressure = force ÷ area; density = mass ÷ volume; the speed of light in a vacuum is about 3 × 10⁸ m/s.

Water freezes at 0 °C (273 K) and boils at 100 °C (373 K); K = °C + 273.