Elements are made up of one type of atom and are organized in the Periodic Table. Examples of elements include: carbon, hydrogen, oxygen and nitrogen. Every element has distinct physical and chemical properties that help scientists to identify them.

Compounds are made up of one or more type of atom (element) which are chemically combined. Compounds form in nature and can be synthesized via a chemical reaction. Compounds have different physical and chemical properties than the elements that they are composed of. Unlike mixtures, compounds cannot be separated by physical means.

Mixtures are formed when two or more elements or compounds are mixed together but not chemically combined. A solution is an example of a mixture. When salt is dissolved in water, water and salt do not chemically combine; they are mixed. Unlike compounds, mixtures can be separated by physical means (ex: evaporation, filtering, etc).

A homogeneous mixture has the same uniform appearance and composition throughout. Many homogeneous mixtures are commonly referred to as solutions. Lemonade is an example of a solution and homogenous mixture.

A heterogeneous mixture is simply any mixture that is not uniform in composition – it's a non-uniform mixture of smaller parts. Using various means, the parts in the mixture can be easily separated from one another.