Gen Chem Final

accuracy

The closeness of a measurement to the actual value.

base unit

(also fundamental unit) A unit that defines the standard for one of the seven physical quantities in the International System of Units (SI).

calibration

The process of correcting for systematic error of a measuring device by comparing it to a known standard.

celsius scale

A temperature scale in which the freezing and boiling points of water are defined as 0°C and 100°C, respectively.

chemical change/chemical reaction

A change in which one or more substances are converted into one or more substances with different composition and properties.

chemical property

A characteristic of a substance that appears as it interacts with, or transforms into, other substances.

chemistry

The scientific study of matter and its properties, the changes it undergoes, and the energy associated with those changes.

combustion

The process of burning in air, often with release of heat and light.

Composition

The types and amounts of simpler substances that make up a sample of matter.

controlled experiment

An experiment that measures the effect of one variable at a time by keeping other variables constant.

conversion

A ratio of equivalent quantities that is equal to 1 and used to express a quantity in different units.

cubic meter

The derived SI unit of volume.

data

Pieces of quantitative information obtained by observation.

density

An intensive physical property of a substance at a given temperature and pressure, defined as the ratio of the mass to the volume: d = m/V.

derived unit

Any of various combinations of the seven SI base units.

dimensional analysis

A calculation method in which arithmetic steps are accompanied by canceling units that represent physical dimensions.

energy

The ability to do work, that is, to move matter. [See also kinetic energy (Ek) and potential energy (Ep).]

exact number

A quantity, usually obtained by counting or based on a unit definition, that has no uncertainty associated with it and, therefore, contains as many significant figures as a calculation requires.

experiment

A set of procedural steps that tests a hypothesis.

extensive property

A property, such as mass, that depends on the quantity of substance present.

gas

One of the three states of matter. Will fill its container regardless of the shape because its particles are far apart.

heat/thermal energy

The energy transferred between objects because of a difference in their temperatures only.

hypothesis

A testable proposal made to explain an observation. If inconsistent with experimental results, a hypothesis is revised or discarded.

intensive property

A property, such as density, that does not depend on the quantity of substance present.

kelvin scale

The preferred temperature scale in scientific work, which has absolute zero (0 K, or − 273.15°C) as the lowest temperature.

kelvin K

The SI base unit of temperature. The kelvin is the same size as the Celsius degree.

kilogram kg

The SI base unit of mass.

kinetic energy Ek

The energy an object has because of its motion.

liquid

One of the three states of matter. Will fill a container to the extent of its own volume and thus forms a surface.

liter

A non-SI unit of volume equivalent to 1 cubic decimeter (0.001 m^3).

mass

The quantity of matter an object contains. Balances are designed to measure.

matter

Anything that possesses mass and occupies volume.

meters

The SI base unit of length. The distance light travels in a vacuum in 1/299,792,458 second.

millimeter mL

A volume (0.001 L) equivalent to 1 cm^3

model/theory

A simplified conceptual picture based on experiment that explains how a natural phenomenon occurs.

natural law

A summary, often in mathematical form, of a universal observation.

observation

A fact obtained with the senses, often with the aid of instruments.

physical change

A change in which the physical form (or state) of a substance, but not its composition, is altered.

physical property

A characteristic shown by a substance itself, without interacting with or changing into other substances.

potential energy

The energy an object has as a result of its position relative to other objects or because of its composition.

precision

(also reproducibility) The closeness of a measurement to other measurements of the same phenomenon in a series of experiments.

property

A characteristic that gives a substance its unique identity.

random error

Error that occurs in all measurements (with its size depending on the measurer's skill and the instrument's precision) and results in values both higher and lower than the actual value.

round off

The process of removing digits based on a series of rules to obtain an answer with the proper number of significant figures (or decimal places).

scientific method

A process of creative proposals and testing aimed at objective, verifiable discoveries of the causes of natural events.

seconds

The SI base unit of time.

SI unit

A unit composed of one or more of the base units of the Système International d'Unités, a revised form of the metric system.

sig figs

The digits obtained in a measurement. The greater the number , the greater the certainty of the measurement.

solid

One of the three states of matter. Has a fixed shape that does not conform to the container shape.

state of matter

One of the three physical forms of matter: solid, liquid, or gas

systematic error

A type of error producing values that are all either higher or lower than the actual value, often caused by faulty equipment or a consistent flaw in technique.

temperature T

A measure of how hot or cold a substance is relative to another substance. A measure of the average kinetic energy of the particles in a sample.

thermometer

A device for measuring temperature that contains a fluid that expands or contracts within a graduated tube.

uncertainty

A characteristic of every measurement that results from the inexactness of the measuring device and the need to estimate when taking a reading.

variable

A quantity that can have more than a single value.

volume V

The amount of space occupied by a sample of matter.

weight

The force that is exerted by a gravitational field on an object and is directly proportional to the object's mass.

amu

anion

A negatively charged ion.

atom

The smallest unit of an element that retains the chemical nature of the element. A neutral, spherical entity composed of a positively charged central nucleus surrounded by one or more negatively charged electrons.

atomic mass

The average of the masses of the naturally occurring isotopes of an element weighted according to their abundances.

amu

A mass exactly equal the mass of 1/12 a carbon-12 atom.

atomic number Z

The unique number of protons in the nucleus of each atom of an element (equal to the number of electrons in the neutral atom). An integer that expresses the positive charge of a nucleus or subatomic particle in multiples of the electronic charge.

atomic symbol

A one- or two-letter abbreviation for the English, Latin, or Greek name of an element.

binary covalent compound

A compound that consists of atoms of two elements, typically nonmetals, in which bonding occurs primarily through electron sharing.

binary ionic compound

A compound that consists of the oppositely charged ions of two elements.

cathode ray

The ray of light emitted by the cathode (negative electrode) in a gas discharge tube; travels in a straight line, unless deflected by magnetic or electric fields.

cation

A positively charged ion.

chemical bond

The force that holds two atoms together in a molecule (or formula unit).

chemical formula

A notation of atomic symbols and numerical subscripts that shows the type and number of each atom in a molecule or formula unit of a substance.

compound

A substance composed of two or more elements that are chemically combined in fixed proportions.

covalent bond

A type of bond in which atoms are bonded through the sharing of electrons; the mutual attraction of the nuclei and an electron pair that holds atoms together in a molecule.

chromatography

A separation technique in which a mixture is dissolved in a fluid (gas or liquid) and the components are separated through differences in adsorption to (or solubility in) a solid surface (or viscous liquid).

covalent compound

A compound that consists of atoms bonded together by shared electron pairs.

crystallization

A technique used to separate and purify the components of a mixture through differences in solubility, resulting in a component coming out of solution as crystals.

dalton da

A unit of mass identical to atomic mass unit (amu).

distillation

A separation technique in which a more volatile component of a mixture vaporizes and condenses separately from the less volatile components.

electron

A subatomic particle that possesses a unit negative charge (− 1.60218 × 10^−19 C) and occupies the space around the atomic nucleus.

element

The simplest type of substance with unique physical and chemical properties. An element consists of only one kind of atom, so it cannot be broken down into simpler substances.

filtration

A method of separating the components of a mixture on the basis of differences in particle size.

formula mass

The sum (in amu) of the atomic masses of a formula unit of a (usually ionic) compound.

formula unit

The chemical unit of a compound that contains the relative numbers of the types of atoms or ions expressed in the chemical formula.

fraction by mass

also mass fraction; The portion of a compound's mass contributed by an element; the mass of an element in a compound divided by the mass of the compound.

group

A vertical column in the periodic table; elements in a group usually have the same outer electron configuration and, thus, similar chemical behavior.

heterogeneous mixture

A mixture that has one or more visible boundaries among its components.

homogenous mixture

A mixture that has no visible boundaries among its components. (also solution)

hydrate

A compound in which a specific number of water molecules are associated with each formula unit.

ion

A charged particle that forms from an atom (or covalently bonded group of atoms) when it gains or loses one or more electrons.

ionic compound

A compound that consists of oppositely charged ions.

isotopes

Atoms of a given atomic number (that is, of a specific element) that have different numbers of neutrons and therefore different mass numbers.

isotopic mass

The mass (in amu) of an isotope relative to the mass of carbon-12.

law of definite composition

A mass law stating that, no matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass.

law of mass conservation

A mass law stating that the total mass of substances does not change during a chemical reaction.

law of multiple proportions

A mass law stating that, if elements A and B react to form two or more compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers.

mass number A

The total number of protons and neutrons in the nucleus of an atom.

mass spectrometry

An instrumental method for measuring the relative masses of particles in a sample by creating charged particles and separating them according to their mass/charge ratios.

metal

A substance or mixture that is relatively shiny and malleable and is a good conductor of heat and electricity. In reactions, metals tend to transfer electrons to nonmetals and form ionic compounds.

metalloid

An element with properties between those of metals and nonmetals.

mixture

Two or more elements and/or compounds that are physically intermingled but not chemically combined.

molecular mass

the sum (in amu) of the atomic masses of the elements in a molecule (or formula unit) of a compound.