Classification of Matter

classification of matterMatter can be defined in a general sense as any physical substance found in our universe. However, a more specific definition, in terms of scientific physics, is anything that occupies space and possesses mass when it is at rest. Mass is the physical property that determines how much gravitational pull an object has, as well as how gravity affects that object. Our whole world is made up of matter, which can be broken down into several different terms and categories. The classification of matter has been generally agreed upon by scientists, and is often represented in the form of a flow chart to be more easily understood. Learning about matter, and discovering how it is commonly classified, is a great way to build a foundation for the study of chemistry, and molecular science in particular.

What Makes Up Matter?

You may already be familiar with the fact that most matter is made up of atoms. Atoms are considered the most basic unit of matter, and when they were first discovered, it was thought that no substance in the universe could be broken down any further than to the atoms it consisted of. However, scientists eventually discovered that atoms are are made up of smaller components known as subatomic particles, including the central nucleus, positively charged protons, negatively charged electrons, and neutrally charged neutrons. The entirety of an atom’s protons and neutrons are contained inside the nucleus, while electrons are situated around the nucleus in what is often called the electron cloud. Electrons are arranged specifically by shells, with each shell containing a unique number of electrons. Atoms of different chemical elements have varying numbers of protons, neutrons, and electrons. For example, an oxygen atom contains eight protons and eight neutrons in the nucleus, and eight electrons in the electron cloud, with two electrons located on the inner shell, and six electrons located on the outer shell. A carbon atom, on the other hand, contains six protons and six neutrons in the nucleus, and six electrons in the electron cloud, with two electrons on the inner shell, and four electrons on the outer shell. Both of these elements have a neutral charge, because they contain the same amount of negative electrons and positive protons. The process by which an atom loses or gains an electron, therefore becoming a charged particle, is called ionization, and the charged particle is referred to as an ion.

Classification of Matter

While atoms and subatomic particles are the basis of matter’s composition, the classification of matter has to do with the variety of substances that are defined as matter. The first step, and most broad distinction, in classifying matter is labeling an example as a substance or a mixture. A substance is something that cannot be separated by physical means. It has constant composition and properties. In other words, it is always chemically built the same way, and always behaves the same way. Water, with the chemical formula H20, is an example of a substance. A mixture, on the other hand, is a combination of substances, specifically substances that do not undergo a chemical reaction when they are combined, so that the chemical properties of each substance are maintained. Salt water is an example of a mixture, as it consists of substances water (H20) and salt (NaCl), but both substances remain the same as they would on their own, and they do not react to each other chemically. Substances and mixtures can be further classified into several sub-categories.

Substances can consist of either chemical elements or chemical compounds. This is determined by whether or not the matter can be broken down and separated by chemical means. Substances that cannot be further broken down by chemical means are elements, which consist of only one kind of atom. There are currently 118 identified chemical elements, listed in the periodic table of elements. They include hydrogen, helium, silver, tin, gold, mercury, radium, plutonium, copper, iron, and nickel. Elements can be divided into metals, non-metals, metalloids, and noble gases. Substances that can be further broken down, however, are compounds. Chemical compounds are made up of more than one kind of atom. Common chemical compounds include carbon dioxide (CO2), methane (CH4), propane (C3H8), and ammonia (NH3).

Mixtures are classified into subcategories based on the consistency with which they are mixed. The subcategories here are homogenous and heterogeneous mixtures. A consistently mixed mixture is classified as homogenous. The composition of a homogenous mixture is totally uniform, and the same chemical properties are evident throughout the mixture. An example of a homogenous mixture is the air in our environment, which is an evenly blended mixture of nitrogen, oxygen, and some other gases. A heterogeneous mixture is not consistently mixed, and the chemical properties of the mixture are not the same throughout. An example of a heterogeneous mixture is sand, which can consist of several different substances that are not consistently mixed. Another example would be oil and water, which tend to separate when mixed together. A third kind of mixture is colloids, which consist of one substance evenly dispersed within another substance. Whipped cream is a colloid, since it is a gas dispersed into a liquid, otherwise known as a foam. Milk is also a colloid, as it is composed of butterfat dispersed within water.

The following chart will provide a visual guide to the classification of matter, beginning with the broader categories and becoming more specific:

Matter – Substances (Pure) or Mixtures (Impure)

Substances – Elements or Chemical Compounds

Elements – Metals, Non-Metals, Metalloids, and Noble Gases

Mixtures – Homogeneous Mixtures, Heterogeneous Mixtures, or Colloids

Understanding Matter and Chemistry

Now that you’ve been introduced to matter and the process by which matter is classified, you can learn more about matter, including different kinds of matter, and about chemistry in general, including the characteristics of the subatomic particles that make up matter. Matter describes nearly everything in our universe, and understanding how it is classified is the foundation for the study of any of the major sciences, including biology, chemistry, and physics.