Chemistry Key Terms


Chemistry is the scientific discipline that studies the properties, composition, structure, and changes of matter. It explores the interactions and transformations of substances at the molecular and atomic levels. Chemistry is often referred to as the central science because it connects and bridges other natural sciences like physics, biology, and environmental science. The primary goals of chemistry include understanding the behavior of matter, explaining the principles governing its changes, and using this knowledge to create new materials and processes for various practical applications.

accuracy: how closely a measurement aligns with a correct value

atom: smallest particle of an element that can enter into a chemical combination

Celsius (°C): unit of temperature; water freezes at 0 °C and boils at 100 °C on this scale

chemical change: change producing a different kind of matter from the original kind of matter

chemical property: behavior that is related to the change of one kind of matter into another kind of matter

chemistry: study of the composition, properties, and interactions of matter

compound:pure substance that can be decomposed into two or more elements

cubic centimeter (cm3 or cc):volume of a cube with an edge length of exactly 1 cm

cubic meter (m3):SI unit of volume

density: ratio of mass to volume for a substance or object

dimensional analysis:(also, factor-label method) versatile mathematical approach that can be applied to computations ranging from simple unit conversions to more complex, multi-step calculations involving several different quantities

element: substance that is composed of a single type of atom; a substance that cannot be decomposed by a chemical change

exact number: number derived by counting or by definition

extensive property: property of a substance that depends on the amount of the substance

Fahrenheit: unit of temperature; water freezes at 32 °F and boils at 212 °F on this scale

gas: state in which matter has neither definite volume nor shape

heterogeneous mixture: combination of substances with a composition that varies from point to point

homogeneous mixture: (also, solution) combination of substances with a composition that is uniform throughout

hypothesis: tentative explanation of observations that acts as a guide for gathering and checking information

intensive property: property of a substance that is independent of the amount of the substance

kelvin (K): SI unit of temperature; 273.15 K = 0 ºC

kilogram (kg): standard SI unit of mass

law: statement that summarizes a vast number of experimental observations, and describes or predicts some aspect of the natural world

law of conservation of matter: when matter converts from one type to another or changes form, there is no detectable change in the total amount of matter present

length: measure of one dimension of an object

liquid: state of matter that has a definite volume but indefinite shape

liter (L):  (also, cubic decimeter) unit of volume; 1 L = 1,000 cm3

macroscopic domain: realm of everyday things that are large enough to sense directly by human sight and touch

mass: fundamental property indicating amount of matter

matter: anything that occupies space and has mass

meter (m): standard metric and SI unit of length; 1 m = approximately 1.094 yards

microscopic domain: realm of things that are much too small to be sensed directly

milliliter (mL): 1/1,000 of a liter; equal to 1 cm3

mixture: matter that can be separated into its components by physical means

molecule: bonded collection of two or more atoms of the same or different elements

physical change: change in the state or properties of matter that does not involve a change in its chemical composition

physical property: characteristic of matter that is not associated with any change in its chemical composition

plasma: gaseous state of matter containing a large number of electrically charged atoms and/or molecules

precision: how closely a measurement matches the same measurement when repeated

pure substance: homogeneous substance that has a constant composition

rounding: procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation

scientific method: path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory

second (s): SI unit of time

SI units (International System of Units): standards fixed by international agreement in the International System of Units (Le Système International d’Unités)

significant figures: (also, significant digits) all of the measured digits in a determination, including the uncertain last digit

solid: state of matter that is rigid, has a definite shape, and has a fairly constant volume

symbolic domain: specialized language used to represent components of the macroscopic and microscopic domains, such as chemical symbols, chemical formulas, chemical equations, graphs, drawings, and calculations

temperature: intensive property representing the hotness or coldness of matter

theory: well-substantiated, comprehensive, testable explanation of a particular aspect of nature

uncertainty: estimate of amount by which measurement differs from true value

unit: standard of comparison for measurements

unit conversion factor: ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit

volume: amount of space occupied by an object

weight: force that gravity exerts on an object

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