13 Classification of Matter (Solid, Liquid, Gas)
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Three States of Matter
The three states of matter are the distinct physical forms that matter can take: solid, liquid, and gas.
LEARNING OBJECTIVES
Describe the three states of matter.
KEY TAKEAWAYS
Key Points
- Matter can exist in one of three main states: solid, liquid, or gas.
- Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around.
- Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is maintained.
- Gaseous matter is composed of particles packed so loosely that it has neither a defined shape nor a defined volume. A gas can be compressed.
Key Terms
- liquid: A substance that flows and keeps no definite shape because its molecules are loosely packed and constantly moving. It takes the shape of its container but maintains constant volume.
- gas: A substance that can only be contained if it is fully surrounded by a container (or held together by gravitational pull); a substance whose molecules have negligible intermolecular interactions and can move freely.
- solid: A substance that retains its size and shape without a container; a substance whose molecules cannot move freely except to vibrate.
The three states of matter are the three distinct physical forms that matter can take in most environments: solid, liquid, and gas. In extreme environments, other states may be present, such as plasma, Bose-Einstein condensates, and neutron stars. Further states, such as quark-gluon plasmas, are also believed to be possible. Much of the atomic matter of the universe is hot plasma in the form of rarefied interstellar medium and dense stars.
Historically, the states of matter were distinguished based on qualitative differences in their bulk properties. Solid is the state in which matter maintains a fixed volume and shape, liquid is the state in which matter adapts to the shape of its container but varies only slightly in volume, and gas is the state in which matter expands to occupy the volume and shape of its container. Each of these three classical states of matter can transition directly into either of the other two classical states.
Solids
A solid’s particles are packed closely together. The forces between the particles are strong enough that the particles cannot move freely; they can only vibrate. As a result, a solid has a stable, definite shape and a definite volume. Solids can only change shape under force, as when broken or cut.
In crystalline solids, particles are packed in a regularly ordered, repeating pattern. There are many different crystal structures, and the same substance can have more than one structure. For example, iron has a body-centered cubic structure at temperatures below 912 °C and a face-centered cubic structure between 912 and 1,394 °C. Ice has 15 known crystal s