Matter occurs in four states: solids, liquids, gases, and plasma. Often
the state of matter of a substance may be changed by adding or removing
heat energy from it. For example, the addition of heat can melt ice into
liquid water and turn water into steam.
Solids
- A solid has a definite shape and volume.
- Examples of solids include ice (solid water), a bar of steel, and dry ice (solid carbon dioxide).
Liquids
- A liquid has a definite volume, but takes the shape of its container.
- Examples of liquids include water and oil.
Gases
- A gas has neither a definite volume nor a definite shape.
- Examples of gases are air, oxygen, and helium.
Some introductory chemistry texts name solids, liquids, and
gases as the three states of matter, but higher level texts recognize
plasma as a fourth state of matter.
Plasma
- Plasma has neither a definite volume nor a definite shape.
- Plasma often is seen in ionized gases. Plasma is distinct from a
gas because it possesses unique properties. Free electrical charges
(not bound to atoms or ions) cause plasma to be electrically conductive.
Plasma may be formed by heating and ionizing a gas.
Stars are made of plasma. Lightning is plasma. You can find plasma inside fluorescent lights and neon signs.
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