Classification of Matter

Atom

The basic unit of a chemical element.

Element

A pure substance that cannot be broken down into simpler substances by chemical means.

Compound

A substance formed when two or more chemical elements are chemically bonded together.

Molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Solid

A state of matter characterized by structural rigidity and resistance to changes of shape or volume.

Liquid

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

Gas

A state of matter with no fixed shape and no fixed volume, expanding to fill its container.

Thermal Energy

The total kinetic energy of particles in a substance.

Kinetic Energy

The energy that an object possesses due to its motion.

Potential Energy

The energy held by an object because of its position relative to other objects.

Attractive Forces

Forces that pull particles together, affecting the state of matter.

Atomic Number

The number of protons in the nucleus of an atom, defining the element.

Atomic Mass (weight)

The weighted average mass of an atom of an element, measured in atomic mass units (amu).

Chemical Symbol

A one or two-letter notation used to represent an element.

Electron

A subatomic particle with a negative charge

Proton

A subatomic particle with a positive charge

Neutron

A subatomic particle with no charge

Subscripts

Numbers written below and to the right of a chemical symbol indicating the number of atoms of an element in a molecule.

Pressure

The force put on an area.

Temperature

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

Volume

The amount of space that a substance takes.

Vaporization

The process of turning from liquid into vapor.

Evaporation

The process of a liquid changing into a gas

Condensation

The process of a gas turning into a liquid.

Melting

The process of a solid turning into a liquid.

Freezing

The process of a liquid turning into a solid.

Sublimation

The process of a solid turning directly into a gas without passing through the liquid state.

Nonmetals

Elements that lack the characteristics of metals.