Chem Beginner

chemistry

The study of matter, its properties, what it is made of, and how it changes.

matter

Anything that has mass and takes up space.

mass

The amount of matter in an object.

volume

The amount of space occupied by an object or substance.

weight

The force exerted on an object by gravity.

substance

Matter with a specific composition and characteristic properties.

pure substance

Matter with a fixed composition that cannot be separated into different substances by physical means.

element

A pure substance made of only one type of atom.

compound

A pure substance made when two or more different elements are chemically bonded together in fixed proportions.

mixture

A combination of two or more substances that are physically combined but not chemically bonded.

homogeneous mixture

A mixture that has a uniform composition throughout.

heterogeneous mixture

A mixture that does not have a uniform composition throughout.

solution

A homogeneous mixture in which one substance is dissolved in another.

solute

The substance that is dissolved in a solution.

solvent

The substance that dissolves the solute.

aqueous solution

A solution in which water is the solvent.

atom

The smallest unit of an element that still has the identity and properties of that element.

molecule

Two or more atoms chemically bonded together.

nucleus

The small, dense center of an atom containing protons and neutrons.

proton

A positively charged particle found in the nucleus of an atom.

neutron

A particle with no electric charge found in the nucleus of an atom.

electron

A negatively charged particle found outside the atomic nucleus.

atomic number

The number of protons in an atom; this number identifies the element.

mass number

The total number of protons and neutrons in an atom.

electron cloud

The region around an atomic nucleus where electrons are likely to be found.

neutral atom

An atom with equal numbers of protons and electrons, giving it no overall electrical charge.

ion

An atom or group of atoms that has gained or lost electrons and therefore has an electrical charge.

cation

A positively charged ion formed when electrons are lost.

anion

A negatively charged ion formed when electrons are gained.

isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

periodic table

A chart that organizes the chemical elements according to atomic number and recurring properties.

element symbol

A one- or two-letter abbreviation representing an element.

period

A horizontal row on the periodic table.

group

A vertical column on the periodic table; elements in the same group often have similar chemical properties.

metal

An element that generally conducts heat and electricity well and is often shiny, malleable, and ductile.

nonmetal

An element that generally does not have the typical properties of metals and often conducts electricity poorly.

metalloid

An element with properties between those of metals and nonmetals.

alkali metal

An element in Group 1 of the periodic table, excluding hydrogen; these metals are generally very reactive.

alkaline earth metal

An element in Group 2 of the periodic table.

transition metal

A metal found mainly in the central portion of the periodic table.

halogen

A reactive nonmetal found in Group 17 of the periodic table.

noble gas

An element in Group 18 that is generally very unreactive.

electron shell

An energy level around an atomic nucleus where electrons can be found.

valence electron

An electron in an atom's outermost occupied energy level that can participate in chemical bonding.

chemical bond

An attractive force that holds atoms or ions together.

ionic bond

A bond caused by the attraction between positively and negatively charged ions.

covalent bond

A bond formed when atoms share electrons.

metallic bond

Bonding in metals involving positive metal ions and mobile electrons.

electron transfer

The movement of one or more electrons from one atom or particle to another.

electron sharing

The sharing of electrons between atoms to form a covalent bond.

ionic compound

A compound made of positively and negatively charged ions held together by electrical attraction.

molecular compound

A compound made of atoms joined primarily by covalent bonds.

chemical formula

A group of chemical symbols and numbers showing which elements are present in a substance.

subscript

A small number in a chemical formula that shows how many atoms of an element are present.

coefficient

A number placed in front of a chemical formula that shows how many units of that substance are involved.

reactant

A starting substance in a chemical reaction.

product

A substance formed during a chemical reaction.

chemical reaction

A process in which atoms are rearranged to form one or more new substances.

chemical equation

A symbolic representation of a chemical reaction.

arrow

In a chemical equation, the symbol showing that reactants form products.

balanced chemical equation

A chemical equation with the same number of each type of atom on both sides.

law of conservation of mass

The principle that matter is not created or destroyed during an ordinary chemical reaction.

physical property

A characteristic that can be observed or measured without changing a substance into a different substance.

chemical property

A characteristic describing a substance's ability to undergo a chemical change.

physical change

A change that does not create a new substance.

chemical change

A change that produces one or more new substances.

state of matter

A physical form in which matter can exist, such as solid, liquid, gas, or plasma.

solid

A state of matter with a definite shape and definite volume.

liquid

A state of matter with a definite volume but no fixed shape.

gas

A state of matter with neither a fixed shape nor a fixed volume.

plasma

A high-energy state of matter containing charged particles.

melting

A change of state from solid to liquid.

freezing

A change of state from liquid to solid.

vaporization

A change of state from liquid to gas.

evaporation

Vaporization that occurs at the surface of a liquid.

boiling

Rapid vaporization occurring throughout a liquid.

condensation

A change of state from gas to liquid.

sublimation

A change of state directly from solid to gas.

deposition

A change of state directly from gas to solid.

temperature

A measure related to the average kinetic energy of particles in a substance.

thermal energy

Energy associated with the motion and interactions of particles in matter.

heat

Thermal energy transferred from a warmer object or system to a cooler one because of a temperature difference.

energy

The ability to cause change or transfer heat or do work.

kinetic energy

Energy associated with motion.

potential energy

Stored energy associated with position, arrangement, or condition.

exothermic

Describing a process that releases energy to the surroundings.

endothermic

Describing a process that absorbs energy from the surroundings.

density

The amount of mass contained in a given volume.

density formula

The relationship density = mass ÷ volume.

physical separation

A method of separating substances in a mixture without changing their chemical identities.

filtration

A separation method that uses a filter to separate a solid from a liquid or gas.

evaporation method

A separation method in which a solvent is removed by vaporization, leaving dissolved material behind.

distillation

A separation method that uses differences in boiling points.

chromatography

A separation method in which substances move at different rates because of differences in their interactions with materials.

measurement

A numerical observation that includes both a number and a unit.

unit

A standard quantity used to describe a measurement.

meter

A unit commonly used to measure length.

liter

A unit commonly used to measure volume.

milliliter

One-thousandth of a liter.

gram

A unit commonly used to measure mass.