chemistry

The study of the composition, structure and properties of matter and the changes it undergoes.

matter

Stuff' that has mass and takes up space.

intensive properties

Characteristics of a substance that do not change with the amount of matter present; e.g., density, color, hardness, melting and boiling point, conductivity, etc.

density

Intensive property, measure of the amount of matter per unit space. Affected by temperature and pressure. d = m / V

melting point

Intensive property, temperature a substance or mixture goes from solid to liquid state. Affected by atmospheric pressure.

boiling point

Intensive property, temperature a substance or mixture goes from liquid to vapor state. Affected by atmospheric pressure.

ductile

Intensive property, able to be formed by drawing out, as in wire production.

malleable

Intensive property, able to be formed by hammering. Bends rather than shatters.

luster

Intensive property, results from substance interacting with light to produce a 'metallic' look.

color

Intensive property, results from substance interacting with visible light.

conductor

Intensive property; substance permits flow of heat and electrical current

insulator

Intensive property; substance resists flow of heat and electrical current.

hardness

Intensive property, measure of the ability of a substance to resist scratching.

extensive properties

Characteristics of a substance that depend on the amount of matter present; e.g., mass, volume, weight,

mass

Extensive property, a measure of the amount of matter contained in a sample.

volume

Extensive property, the amount of space an object occupies. Affected by temperature and pressure

atom

The smallest unit of chemical matter.

pure substance

Substance containing only one type of element or compound.

mixture

Two or more pure substances found together, each keeping its own identity and properties. Can be separated by physical means.

homogeneous mixture

A mixture with identical composition at any sampling point, e.g., salt water, metal alloys, air.

heterogeneous mixture

A mixture with varied composition depending on where you take a sample, e.g. Rocky Road ice cream, a load of sand and gravel, a mixture of sawdust and iron.

element

A pure substance made up of only of one kind of atom. Can not be further separated by physical or chemical means.

metal

Elements that are good conductors of heat and electricity, malleable, ductile, have luster. >75% of elements are metals.

metalloids (semi-metals)

Substances with some properties characteristic of metals and some characteristic of nonmetals.

non-metal

Elements that are poor conductors of heat and electricity, neither malleable nor ductile, generally located on the right-hand side of the periodic table.

compound

Substance formed by atoms of two or more elements, chemically bonded.

chemical bond

Force between two atoms which holds them together.

molecule

Two or more atoms, chemically bonded, that display the properties of that element or compound.

states of matter

Physical form of a substance. Three most common are sollid, liquid and gas. Plasma and Bose-Einstein condensate, are two other states of matter not normally experienced directly.

solid

State of matter having both definite shape and definite volume.

liquid

State of matter having definite volume but indefinite shape.

gas

State of matter having neither definite shape nor definite volume.

physical change

Change in a property of a substance that does not change the identity of the substance. E.g., melting, crushing, vaporization,

chemical change

Change in which two or more pure substances react to form new substances with different chemical composition and properties.

law of conservation of energy

Energy cannot be created or destroyed, it can only change form.

law of conservation of mass

All elements present at the beginning will be present at the end of a chemical reaction; only bonding arrangements will change.