Matter on the Move

Students explore the particle model of matter in regards to solids, liquids, and gases.


In this lesson we will be exploring the particle model of matter. All matter is made up of particles. Particles are made up of atoms and molecules.


  • Solids
    • Particles in solids are tightly packed together and cannot freely move around, instead particles in a solid will vibrate.
  • Liquids
    • Particles in liquids freely move around, often in clusters with other particles. These particles cannot hold a definite shape because they can freely move around each other and will take the shape of the container they are in.
  • Gases
    • Particles in gases freely move around and are so far apart that they can seem like an empty space. Most gases are invisible to the human eye, but they do attempt to evenly distribute across a container.

Changes in States

As energy is added or removed from particles a change of state may occur. All matter has multiple states. There are three states of matter that we will be exploring:

  • Solids
    • A state of matter that has a definite shape and volume.
  • Liquids
    • A state of matter that has a definite volume, but no definite shape.
  • Gases
    • A state of matter that does not have a definite shape or volume.

Look at the image below to explore the different state changes and their associated names.


  • Condensation: Condensation is the change of the physical state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. Source
  • Vaporization: Vaporization of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon. Source
  • Melting (Fusion): Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance’s temperature to the melting point. Source
  • Freezing (Solidification): Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid or the liquid content of a substance, usually due to cooling. Source
  • Sublimation: Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. Source
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