What is Matter?

Nothing. What’s the matter with you?

Matter is defined as anything that has mass and takes up space.

Mass is the quantity of matter an object contains and is measured in grams (g) and kilograms (kg). Mass is not to be confused with weigh, which is the force exerted on an object by gravitational attraction. In physics, mass is defined as being directly proportional (straight line graph through the origin) to the force required to change its speed of direction. Basically, matter is something that can be touched, like metal, people, or apples. Energy, light and sound are not examples of matter.

There are three states of matter: gas, liquid, and solid. There are actually five states in total but the last two are for the hardcore physicists and chemists and are generally beyond the scope of biochemistry.

Solids are rigid and have fixed shapes and volumes. Liquids have fixed volumes but can flow freely to match their container. Gases have neither fixed shapes nor fixed volumes and expand to fill their containers. Matter can change between these states. The processes are summarized in the image below.

Pure Substances and Mixtures

A pure substance is matter that has definite and constant composition and has distinct chemical properties. An example of a pure substance is a diamond. There are two types of pure substances. An element is a substance that cannot be broken down into simpler substances or changed chemically. All of the known elements are in the periodic table. A compound is a combination of two or more elements that are in fixed proportions. Pure substances are not as commonly found in nature as mixtures are.

A mixture is a combination of two or more pure substances in a such a way that no chemical reaction occurs. Mixtures can be further classified as homogeneous or heterogeneous. Homogeneous mixtures, also known as solutions, are mixtures in which all the proportions of the mixture are in the same state. An example of this is the air we breathe. Homogeneous mixtures of metals are more commonly referred to as alloys. Mixtures that have non-uniform composition (i.e. mixtures that are not all in the same state) are known as heterogeneous mixtures. Dirt is an example of a heterogeneous mixture.

Mixtures can be separated in several ways:

  • Filtration – separation of solids based on size
  • Evaporation – removal of liquids from solids
  • Chromatography – separates mixtures on a solid surface with addition of solvent
  • Distillation – separation of liquids based on different boiling points
  • Crystallization – separates mixtures based on differences in solubility

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