Introduction to Chemistry

matter

anything that has mass and takes up space

chemistry

the study of matter and how matter changes

element

a substance that cannot be broken down into any other substances by chemical or physical means

molecule

a group of two or more atoms held together by chemical bonds

chemical formula

shows the elements in the compound and the ratio of atoms

mixture

made of two or more substances in the same place, but their atoms are not chemically bonded

density

the ratio of the mass of a substance to its volume

solid

has a definite shape and a definite volume

liquid

a state of matter that has no definite shape but has a definite volume

gas

a state of matter with no definite shape or volume

surface tension

an inward pull among the molecules on the surface in a liquid

viscosity

a liquid's resistance to flowing

pressure

the force of a gas's outward push on the walls of its container

atom

the smallest particle of an element that can still be considered an element

electron

negatively charged atomic particle

proton

positively charged particle in an atom's nucleus

neutron

an atomic particle with no charge

atomic number

the number of protons in the nucleus of an atom

period

a row in the periodic table

group

elements in the same vertical column in the periodic table

metal

elements that are good conductors of heat and electric current

luster

shiny and reflective

malleable

material can be hammered or rolled into flat sheets

ductile

material can be pulled out into long wires

thermal conductivity

ability of an object to transfer heat

electrical conductivity

ability of an object to carry electric current

nonmetal

element that lacks most of the properties of a metal

metalloid

have some properties of metals and some properties of nonmetals

valence electron

the electron in the highest energy level of an atom and that are involved in chemical bonding

ion

an atom that has become electrically charged

ionic compound

a compound that consists of positive and negative ions

covalent bond

a chemical bond formed when two atoms share electrons

molecular compound

a compound that is composed of molecules

double bond

a chemical bond formed when atoms share two pairs of electrons

triple bond

a chemical bond formed when atoms share three pairs of electrons

alloy

a mixture of two or more elements, at least one of which is a metal

reactant

a substance that enters into a chemical reaction

product

a substance formed as a result of a chemical reaction

law of conservation of mass

The principle that the total amount of matter is neither created nor destroyed during any chemical or physical change.

synthesis

A chemical reaction in which two or more simple substances combine to form a new, more complex substance

decomposition

A chemical reaction that breaks down compounds into simpler products

replacement

A reaction in which one element replaces another in a compound or when two elements in different compounds trade places

activation energy

the minimum amount of energy needed to start a chemical reaction

solution

a mixture containing a solvent and at least one solute that has the same properties throughout

colloid

a mixture containing small, undissolved particles that do not settle out

suspension

a mixture in which particles can be seen and easily separated by settling or filtration

acid

a substance that tastes sour, reacts with metals and carbonates, and turns blue litmus paper red

base

a substance that tastes bitter, feels slippery, and turns red litmus paper blue

indicator

a compound that changes color in the presence of an acid or base