Basic Chemistry/States of matter

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Matter exists in four different forms - solid, liquid, gas, and plasma. These are the four states of matter. You can recognize each state because they have different properties. A property of a material describes how it behaves. This behavior is not observable at the chemical level due to microscopic sized particles. We can observe how many H2O particles behave when we open a faucet, releasing water, which is a lot of H2O particles in their liquid state. Of course we can observe other states of H2O particle groupings, at low temperatures they freeze, demonstrating a solid property. At high temperatures they form a gas called steam.

Readings[edit | edit source]

  1. Wikipedia: State of matter
  2. Wikipedia: Solid
  3. Wikipedia: Liquid
  4. Wikipedia: Gas

States of matter[edit | edit source]

Property Solids Liquids Gases
Volume has definite volume has definite volume has no definite volume-always fills the container they are in
Shape have a definite shape match the shape of the container become the same shape as the container
Density have a high density have a high density have a low density
Compressibility not easily squashed not easily squashed easily squashed
Flow don't flow flow easily flow easily

Particle theory[edit | edit source]

  • All materials are made up of particles.
  • The particles that are in a substance (material) stay the same whatever state the substance is in. The only thing that changes is the arrangement of the particles and the energy they have.
  • Whichever state the substance is in depends on how strongly the particles stick together. And how well the particles stick together depends on:
    • the material
    • the temperature
    • the pressure.
  • This is particle theory, and it explains all the different properties of solids, liquids and gases.

Solids[edit | edit source]

  • They are held tightly together by strong forces of attraction.
  • They are held in fixed positions but they do vibrate.
  • Because the particles don't move, solids have a definite shape and volume, and can't flow.
  • Because the particles are already packed closely together, solids can't easily be compressed.
  • Because there are lots of particles in a small volume, solids are dense.
  • Powdered solids cannot take the shape of their container.

Liquids[edit | edit source]

  • Particles are still touching and held by very strong forces of attraction.
  • They are free to move past each other.
  • Because the particles can move, liquids don't have a definite shape, and they can flow.
  • Because the particles are still packed close together, liquids can't easily be compressed and keep the same volume.
  • Because there are lots of particles in a small volume, liquids have almost the same density as when they are solid. Some, like water are actually more dense than their solid, but most are very slightly less dense.

Gases[edit | edit source]

  • Particles are far apart from each other because there are very weak forces of attraction between them.
  • They move fast in all directions.
  • Because of this, gases don't have a definite shape or volume and fill any container.
  • Because there is lots of free space between particles, gases can easily be compressed.
  • Because there aren't many particles in a large volume, gases have very low densities typically 1000 times less than in their condensed state as solid or liquid at atmospheric temperature and pressure.