USAC PCB Guatemala flashcards

25 cards. Read the term and the definition here. The deck at the top of this page is optional.

tema

Idea central o asunto del que trata un texto, que se puede enunciar en una frase y se distingue de los temas secundarios que lo acompañan.

tesis

Postura o afirmación principal que el autor defiende en un texto argumentativo; suele aparecer en la introducción o el cierre y el resto del texto la sostiene.

resumen

Reformulación breve y fiel del contenido de un texto, con las ideas esenciales y sin opiniones ni detalles accesorios, respetando el orden lógico del original.

coherencia

Propiedad textual por la que las ideas se organizan en torno a un tema con una progresión lógica, sin contradicciones ni saltos que rompan el sentido global.

cohesión

Conjunto de mecanismos lingüísticos (conectores, pronombres, elipsis, repeticiones léxicas) que enlazan las oraciones y párrafos de un texto para que se lean como una unidad.

Variable

A symbol representing a quantity whose permitted values must follow the stated domain and the units of the problem rather than an unstated assumption.

Domain

The allowed inputs or values for a mathematical statement, including any restrictions from the context, a denominator, an even root or a count.

Equation

A claim that two expressions have equal values, whose solutions must make the original relation true and satisfy the declared restrictions.

Inequality

A comparison describing values above or below a boundary, with inclusion or exclusion of the boundary indicated by the relation used.

Function

A rule or relation assigning each permitted input exactly one output, distinguished from a general relation that may assign multiple outputs to one input.

Water potential

Water chemical potential expressed relative to a defined pure-water reference, often in pressure units. Pure water at reference conditions is assigned zero; positive pressure can raise potential, and water moves toward lower potential.

Osmosis

The net movement of water across a partially permeable membrane from a region of higher water potential to one of lower water potential. It is passive and driven by the water potential gradient.

Solute potential

The component of water potential caused by dissolved solutes, always negative or zero. More concentrated solutions have more negative solute potentials and so attract water.

Plasmolysis

Shrinking of the protoplast away from the plant cell wall when a cell loses water in a hypertonic solution. It occurs because the protoplast contracts while the rigid wall stays in place.

Facilitated diffusion

Passive movement through membrane channels or carriers down an electrochemical gradient. The transport step does not directly hydrolyze ATP, although other processes may use energy to establish the gradient.

Atomic number

The number of protons in the nucleus of an atom, which uniquely identifies the element. In a neutral atom it also equals the number of electrons.

Mass number

The total count of protons plus neutrons in one atom's nucleus. It is a whole number written as a superscript beside the element symbol and differs between isotopes.

Isotope

One of two or more atoms of the same element that have equal proton counts but different neutron counts, so they differ in mass while sharing nearly identical chemical behaviour.

Relative atomic mass

The weighted average mass of an element's atoms compared with one-twelfth the mass of a carbon-12 atom, taking natural isotopic abundance into account. It is dimensionless and rarely a whole number.

Aufbau principle

The rule that electrons occupy the lowest-energy available orbitals first when an atom is built up, giving the familiar 1s 2s 2p 3s filling order and the ground-state configuration.

Displacement

The straight-line distance and direction of a point from its starting position, treated as a vector quantity. It differs from distance travelled, which is a scalar and ignores direction.

Velocity

The rate of change of displacement with respect to time, a vector quantity with both magnitude and direction. Average velocity divides total displacement by total time taken.

Acceleration

The rate at which velocity changes with time, including changes in speed, direction, or both. It is measured in metres per second squared and is a vector.

Newton's second law

The resultant force on a body equals the rate of change of its momentum; for constant mass this reduces to force equals mass times acceleration, measured in newtons.

Momentum

The product of a body's mass and its velocity, a vector measured in kilogram metre per second. For a chosen system, total momentum is conserved when the net external impulse is zero; closure to matter alone does not establish isolation from force.