ECAT key terms

The rate at which an object's velocity changes with time. It is a vector quantity, measured in metres per second squared, and can involve speeding up, slowing down, or changing direction.

The principle that the net force on an object equals its mass multiplied by its acceleration. A larger force produces greater acceleration, while a heavier mass resists acceleration.

A push or pull that can change an object's motion, shape, or direction. It is a vector quantity measured in newtons and arises from interactions such as contact or gravity.

The rate of change of an object's displacement with time, including its direction. Unlike speed, it is a vector, so reversing direction changes velocity even if speed stays constant.

The product of an object's mass and its velocity. It measures how hard an object is to stop and is conserved in a closed system during collisions.

The energy transferred when a force moves an object through a distance in the direction of the force. It is calculated as force times displacement and measured in joules.

The rate at which work is done or energy is transferred. It equals work divided by time and is measured in watts, where one watt is one joule per second.

The energy an object possesses because of its motion. It depends on mass and the square of speed, so doubling speed quadruples the kinetic energy.

Stored energy that an object has because of its position or configuration, such as height in a gravitational field or compression of a spring. It can convert into kinetic energy.

The relationship stating that current through a conductor is directly proportional to the voltage across it, provided temperature stays constant. It is written as voltage equals current times resistance.

The rate of flow of electric charge through a conductor, measured in amperes. One ampere corresponds to one coulomb of charge passing a point each second.

The distance between two consecutive corresponding points on a wave, such as crest to crest. It is usually measured in metres and relates to frequency and wave speed.

The number of complete oscillations or wave cycles passing a point each second, measured in hertz. Higher frequency means more cycles occur in a given time.

The bending of a wave as it passes from one medium into another where its speed changes. Light bends toward the normal when entering a denser medium.

The amount of a substance containing as many elementary particles as there are atoms in twelve grams of carbon-12, approximately 6.02 times ten to the twenty-third.

The mass of one mole of a substance, expressed in grams per mole. It is found by summing the atomic masses of all atoms in the formula.

The simplest whole-number ratio of atoms of each element present in a compound. It may differ from the molecular formula, which gives the actual number of atoms.

A chemical process in which a substance loses electrons, often gaining oxygen or losing hydrogen. Oxidation and reduction always occur together in redox reactions.

A chemical process in which a substance gains electrons, often losing oxygen or gaining hydrogen. It is the counterpart of oxidation and occurs simultaneously with it.

A reaction involving the transfer of electrons between species, so that one substance is oxidised while another is reduced. Oxidation states of the elements involved change.

A substance that donates protons or hydrogen ions in solution, lowering pH below seven. Acids react with bases to form salts and water in neutralisation reactions.

A substance that accepts protons or hydrogen ions, or releases hydroxide ions in solution. Bases neutralise acids and typically have a pH above seven.

A scale from zero to fourteen expressing the acidity or alkalinity of a solution. It equals the negative logarithm of hydrogen ion concentration, with seven being neutral.

A substance that increases the rate of a chemical reaction by lowering its activation energy without being consumed. It speeds up the reaction but does not change the equilibrium position.

The minimum energy that colliding particles must possess for a chemical reaction to occur. A lower activation energy means the reaction proceeds faster at a given temperature.

An atom of the same element with the same number of protons but a different number of neutrons. Isotopes share chemical properties but differ in mass number.

A chemical bond formed when two atoms share one or more pairs of electrons. It typically occurs between non-metals and produces discrete molecules or network structures.

The electrostatic attraction between oppositely charged ions formed when one atom transfers electrons to another. It usually occurs between metals and non-metals.

The instantaneous rate of change of a function with respect to a variable, representing the slope of the tangent to its graph at a point.

The accumulated total of a function over an interval, interpreted as the area under its curve. Integration is the reverse process of differentiation.

The value that a function approaches as its input approaches a particular point. Limits underpin the definitions of derivatives and integrals in calculus.

A rectangular arrangement of numbers in rows and columns. Matrices can be added, multiplied, and inverted, and are used to solve systems of linear equations.

A single scalar value computed from a square matrix that indicates whether the matrix is invertible. A zero determinant means the matrix has no inverse.

A quantity possessing both magnitude and direction, often represented as an arrow or an ordered list of components. Vectors can be added and scaled.

An arrangement of items in which the order matters. The number of permutations of n distinct items taken r at a time is n factorial divided by n minus r factorial.

A selection of items from a group in which order does not matter. Its count is given by the binomial coefficient, equal to n factorial divided by r factorial times n minus r factorial.

A measure between zero and one of how likely an event is to occur. It equals the number of favourable outcomes divided by the total number of equally likely outcomes.

A word that has the same or nearly the same meaning as another word in the same language, such as big and large. Synonyms help avoid repetition in writing.

A word that expresses the opposite meaning of another word, such as hot and cold. Antonyms are used to create contrast in expression.

A figure of speech that describes something by directly stating it is something else, without using like or as. For example, calling time a thief.

A figure of speech that compares two different things using the words like or as. For example, describing someone as brave as a lion.

The grammatical rule that a verb must match its subject in number and person. A singular subject takes a singular verb, while a plural subject takes a plural verb.

A group of words containing a subject and a verb. An independent clause expresses a complete thought, while a dependent clause cannot stand alone as a sentence.