8th Grade State Test Review

matter

Anything that has mass and takes up space

mass

A measure of the amount of matter in an object

volume

A measure of the size of a body or region in three-dimensional space

density

Mass per unit volume

pure substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

atom

Smallest unit of matter that retains the properties of an element

element

A pure substance made of only one kind of atom

compound

A substance made up of atoms of two or more different elements joined by chemical bonds

mixture

A combination of two or more substances that are not chemically combined

solution

A mixture that forms when one substance dissolves another

suspension

A heterogeneous mixture that separates into layers over time

homogeneous

Describes something that has a uniform structure or composition throughout

heterogeneous

A mixture that is not uniform throughout

physical properties

Characteristics of matter that can be seen through direct observation such as density, melting point, and boiling point.

chemical properties

A property or characteristic of a substance that is observed during a reaction in which the chemical composition or identity of the substance is changed.

freezing

A change of state of matter from a liquid to a solid by the loss of heat

melting

Temperature at which a solid becomes a liquid

evaporation

The change of a liquid to a gas

solid

A form of matter that has a definite shape and volume

liquid

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

gas

A state of matter with no definite shape or volume

plasma

A gas-like state of matter consisting of a mixture of free electrons and atoms that are stripped of their electrons

chemical bond

An attractive force that holds together the atoms, ions, or groups of atoms in a molecule or compound.

covalent bond

A bond that forms when atoms share electrons.

ionic bond

Formed when one or more electrons are transferred from one atom to another

cation

A positively charged ion

anion

A negatively charged ion

protons

A positively charged particle in the nucleus of an atom

neutrons

A subatomic particle that has no charge and that is found in the nucleus of an atom

atomic number

Number of protons in an atom

atomic mass

Number of protons and neutrons found within the nucleus of an atom

pH

measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14. 0 is most acidic + and 14 is most basic + or alkaline.

acid

A substance with a pH below 7

base

A substance with a pH above 7

indicator

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