The States of Matter

The States of Matter

Matter is usually classified into one of three states or phases: solid, liquid, or gas.

Because they can flow easily, both liquids and gases are called fluids.

• A solid has a fixed shape which it tends to retain, whereas fluids have no fixed shape.
• A liquid sinks to the bottom of its container, and a gas expands to fill the available volume.
• The atoms in a solid vibrate about fixed equilibrium positions, whereas the atoms or molecules in a liquid move about relatively freely and collide frequently with each other.
• The atoms in a solid or liquid are quite closely packed, which makes it difficult to reduce their volume, they are almost incompressible.
• On the average, the atoms or molecules in a gas are far apart, typically about ten atomic diameters at room temperature and pressure. They collide much less frequently than those in a liquid. Gases in general are compressible.