DAT PAT key terms

A flat, overhead view in which raised and sunken areas are shown by outline shape and by relative position, so that a hole looks identical to a hill until shading or layering is considered.

The open space inside a closed outline, such as the gap inside a keyhole or between two joined shapes. Counting and closing apertures is a common way to match an object to its rotated version.

A perceptual task in which a sheet is folded, holes are punched through the layers, and the unfolded sheet must be predicted. Each punch appears once in every layer, mirrored across each fold line.

Determining how many identical cubes make up a stacked figure, including cubes hidden behind and beneath visible ones. Every cube must be supported, so columns are counted from the ground up.

Ordering several drawn angles from smallest to largest without a protractor. Success depends on comparing how far each pair of rays opens apart, not on the length of the drawn rays.

A view of a three-dimensional object from a fixed direction, such as front, top, or side, with no perspective distortion. Matching these views to a drawn solid tests spatial visualization.

A property in which one half of a figure is the mirror image of the other across a line. Recognizing it quickly helps predict where punched holes reappear after a fold is opened.

The ability to match a shape to an identical or rotated copy of itself, or to pick the piece that completes a larger pattern. Distractors usually differ by one altered edge or proportion.

The blocking of one object by another that lies in front of it. The blocked object is perceived as farther away, which is a strong depth cue in three-dimensional figures.

The number of moles of solute dissolved per liter of solution. It changes with temperature because the solution volume expands, unlike molality, which is based on the mass of solvent.

The amount of a substance containing 6.022 times 10 to the 23rd particles. It converts between mass and number of particles using molar mass as the bridge.

The reactant that is used up first and therefore caps the amount of product formed. Identifying it requires comparing the mole ratio supplied with the ratio demanded by the balanced equation.

The actual mass of product obtained divided by the theoretical mass predicted from stoichiometry, multiplied by 100. Values below 100 percent reflect side reactions, incomplete reaction, or loss during handling.

A system at equilibrium shifts to partly offset a stress such as added reactant, removed product, changed pressure, or changed temperature. Only temperature changes alter the value of the equilibrium constant itself.

The ratio of product concentrations to reactant concentrations, each raised to its balanced-equation coefficient, at equilibrium. A large value favors products; a small value favors reactants.

The negative base-ten logarithm of hydrogen ion concentration. Each unit represents a tenfold change in acidity, so a pH of 3 is one hundred times more acidic than a pH of 5.

A solution of a weak acid and its conjugate base, or a weak base and its conjugate acid, that resists pH change when small amounts of strong acid or base are added.

The minimum energy colliding molecules must possess for a reaction to proceed. Catalysts lower it by providing an alternate pathway without changing the overall energy difference between reactants and products.

A substance that speeds a reaction by lowering its activation energy and is regenerated unchanged. It does not shift the equilibrium position or change the enthalpy of the reaction.

Adding solvent to a solution to lower its concentration while keeping the amount of solute constant. The relation initial molarity times initial volume equals final molarity times final volume applies.

A procedure in which a solution of known concentration is added until the analyte is exactly neutralized, often signaled by an indicator color change. Moles of titrant then give moles of analyte.

Division producing two genetically identical daughter cells, used for growth and repair. Its stages are prophase, metaphase, anaphase, and telophase, followed by cytokinesis.

Two successive divisions that halve the chromosome number and generate genetically varied gametes. Crossing over in prophase one and independent assortment in metaphase one are the main sources of variation.

One of the alternative versions of a gene at a given locus. An organism inherits two per locus in diploid cells, and their combination determines the expressed phenotype.

The particular pair of alleles an organism carries at a locus, written as two letters such as homozygous dominant, heterozygous, or homozygous recessive. It interacts with environment to produce phenotype.

A grid used to predict offspring genotype ratios from parental gametes. Each axis lists the possible gametes of one parent, and each cell combines one gamete from each side.

Differential survival and reproduction of individuals whose inherited traits better suit their environment. Over generations it changes allele frequencies in a population, producing adaptation.

Body parts in different species sharing common ancestry but possibly differing in function, such as the forelimbs of humans, whales, and bats. They provide evidence of evolutionary relationship.

Net movement of water across a selectively permeable membrane from lower solute concentration to higher solute concentration. It continues until solute concentrations equalize or pressure stops the flow.

Spontaneous net movement of particles from a region of higher concentration to lower concentration, driven by random molecular motion. It requires no energy input and no membrane.

The ability of an external solution to cause a cell to gain or lose water. A hypertonic solution shrinks a cell, a hypotonic one swells it, and an isotonic one leaves volume unchanged.

The central claim a passage is built to support, usually stated or implied in one or two sentences. It is broader than any single detail but narrower than the general topic.

A specific fact, example, or statistic that explains or backs up the main idea. Detail questions ask what the passage states directly, so the answer must be traceable to the text.

A conclusion that follows logically from stated information but is not written outright. Valid inferences need textual support; they are not guesses or personal opinions.

The author's attitude toward the subject, conveyed through word choice and sentence structure. Common labels include critical, neutral, enthusiastic, skeptical, and nostalgic.

A comparison of two quantities by division, often written as a fraction or with a colon. Scaling both parts by the same factor leaves the ratio unchanged.

An equation stating that two ratios are equal. Solving one usually means cross-multiplying and isolating the unknown quantity.

A rate expressed per one unit of the second quantity, such as cost per item or distance per hour. It makes comparisons between different-sized packages or trips straightforward.

The long-run fraction of trials in which an event occurs, computed for equally likely outcomes as favorable outcomes divided by total outcomes. Values always lie between zero and one.

A selection of items in which order does not matter. The count equals the factorial of the total divided by the factorial of the chosen number times the factorial of the remainder.

An arrangement of items in which order matters. The count equals the factorial of the total divided by the factorial of the unchosen remainder.