A change that occurs when one or more substances change into entirely new substances with different properties.

The law that states that mass cannot be created or destroyed in ordinary chemical and physical changes.

The smallest unit of an element that maintains the properties of that element.

An atom's central region, which is made up of protons and neutrons.

A subatomic particle that has a positive charge and that is located in the nucleus of an atom; the number of protons in the nucleus is the atomic number, which determines the identity of an element.

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

A region around the nucleus of an atom where electrons are likely to be found.

A subatomic particle that has a negative charge.

A substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number.

A one-, two-, or three-letter abbreviation of the name of an element.

The number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element.

The sum of the numbers of protons and neutrons in the nucleus of an atom.

One of two or more atoms that have the same number of protons (atomic number) but different numbers of neutrons (atomic mass).

An arrangement of the elements in order of their atomic numbers such that elements with similar properties fall in the same column, or group.

A vertical column of elements in the periodic table; elements in a group share chemical properties.

In chemistry, a horizontal row of elements in the periodic table.

The process in which atoms are rearranged to produce a new substance.

The reaction of an acid and a base to form a neutral solution of water and a salt.

A combination of chemical symbols and numbers to represent a substance.

An expression that represents a chemical reaction.

A chemical reaction that absorbs energy, usually as heat.

A chemical reaction that releases energy, usually as heat or light.

A substance that participates in a chemical reaction.

A substance that forms in a chemical reaction.

The law that states that energy cannot be created or destroyed but can be changed from one form to another.

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

A homogeneous mixture throughout which two or more substances are uniformly dispersed.

Anything that has mass and takes up space.

The study of matter

Type of matter with fixed composition

Substance made of two or more elements, chemically combined in a fixed proportion.

Heterogeneous mixture with particles that are larger than those in solutions, but not heavy enough to settle out.

Heterogeneous mixture containing a liquid in which visible particles settle out.