IN THE THREE MAIN PHASES OF MATTER MOLECULES ARE:
  • SOLID
    • SLOW MOVING, LOW ENERGY
    • DO NOT FLOW
    • HIGHLY STRUCTURED
  • LIQUID
    • MOVE FASTER THAN SOLID
    • FLOW EASILY
    • LESS STRUCTURE THAN SOLID
  • GAS (VAPOR)
    • VERY FAST, HIGH ENERGY
    • FLOW EASILY
    • NO STRUCTURE
The following diagram shows what happens when a substance goes through a phase change. For instance: When solid water (ice) undergoes a phase change to Liquid (phase change name: melting!)
    The following occurs when ice melts:
    • the molecules in the SOLID PHASE absorb energy from their surroundings (gains energy)
    • they begin to vibrate (move) more and more (they speed up) until...
    • they become less structured and enter the LIQUID PHASE
Notice that the more structured a phase is, the closer to the left of the diagram it is.
The phases to the left side also contain lower energy and have less molecular motion.
(Remember that heat is related to the internal energy of molecular motion the "vibration" of the molecules.)
The opposite occurs when a phase change from an LESS STRUCTURED phase (ie. a liquid) changes to a MORE STRUCTURED phase (ie. a solid)
    The following occurs when liquid freezes:
    • the molecules in the LIQUID PHASE give off energy to their surroundings (loses energy)
    • they begin to vibrate (move) less and less (they slow down) until ...
    • they become more structured and enter the SOLID PHASE
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