Characteristics of the Four States

When we look at an object, it is obvious to us what class of matter it belongs to: that chair is a solid, the drink sitting on the kitchen table is a liquid, and the air we breathe is a gas. However, under strange or severe conditions, such as extremely low temperature and high pressure, the lines between the states can blur. Therefore, scientists have given precise definitions to each phase of matter:

• Solids: Solids have both fixed volume and fixed shape, and they retain that shape regardless of their container. In solids, atoms or molecules are locked into a particular arrangement and are not free to move about.
• Liquids: Liquids have fixed volume but conform to the shape of their container. In liquids, atoms or molecules are free to move around inside the liquid, but are still strongly attracted to other atoms or molecules around them.
• Gases: Gases have neither fixed volume nor fixed shape; they expand to fill their entire container. Gas atoms or molecules are widely separated, and the attraction between them is small.
• Plasmas: Plasmas occur when a gas is heated so strongly that the electrons are stripped away from their atoms, creating a hot soup of free-floating atomic nuclei and electrons. Rare on earth, plasmas are the dominant state of matter in stars. Because temperatures are so high,
• Solutions: This state of matter involves solute molecules (usually of a gas or solid) that adhere to the molecules of a solvent. Because the solute and solvent are bound together, both have different properties than usual.

We will begin by discussing the properties of solids, starting with the various types of solid.

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