Final answer:
Air is a mixture of gases; an element is a pure substance made of one type of atom; a molecule is a composition of two or more atoms; and a mixture is a combination of substances that are not chemically bonded.
Step-by-step explanation:
Understanding Air, Elements, Molecules, and Mixtures
Air is composed of multiple gases including nitrogen, oxygen, argon, carbon dioxide, and trace amounts of other gases. It is essentially a mixture because it contains different substances that are not chemically bonded together.
Definitions
An element is a substance that is made up of only one type of atom and cannot be separated into simpler substances by ordinary chemical means. Iron is an example of an element.
A molecule is a composition of two or more atoms that act as a unit. This can be in the form of a single element with multiple atoms like O₂, or a compound with different atoms like H₂O.
A mixture is a combination of two or more elements or compounds which have not reacted to bond together; each part of the mixture retains its own properties.
Blood and air are examples of mixtures, with air being homogeneous as its components are evenly distributed, and blood can also be considered a homogeneous mixture under certain analyses.
Classifications
Element: a pure substance consisting of a single type of atom. Example: Gold.
Compound: a substance that has two or more types of atoms bonded together. Example: Carbon dioxide.
Mixture: consists of a combination of elements or compounds that are not chemically bonded. Example: Soil (heterogeneous) and salt water (homogeneous).