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Phases of Matter

Phases of Matter. Solids. Particles are tightly packed in an orderly pattern . Can’t move about. Can only shake or vibrate. Memory Jogger. Gases. Particles are far apart and can move rapidly from place to place.

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Phases of Matter

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  1. Phases of Matter

  2. Solids • Particles are tightly packed in an orderly pattern. Can’t move about. Can only shake or vibrate. Memory Jogger

  3. Gases • Particles are far apart and can move rapidly from place to place. • Gases can move from place to place (translation), they can tumble (rotation), & they can shake (vibration). Memory Jogger

  4. Liquids • There is a little space between particles & they can slide past each other. Little or no order. • Liquids can vibrate & have very hindered translation and rotation – the particles can move a little bit but then they bump into a neighbor.

  5. Liquids Condensed phases = liquid & solid phases. Particles are close together.

  6. Kinetic Energy • Atoms & molecules are in constant motion. • Temperature is an assessment of the average K.E. of the particles in a sample of matter. • If the temperature , the avg. K.E. • If temperature , then avg. K.E. Memory Jogger  

  7. Temperature vs. Motion • A gas & a solid at the same temp have the same avg. K.E., but the particles in the 2 phases move very differently.

  8. Why do liquids & solids exist? What holds them together?

  9. Intermolecular Forces • There are attractive forces between all particles of matter called intermolecular forces. • Intermolecular forces arise because atoms contain charged particles – protons & electrons. • Not as strong as bonding within a molecule, but intermolecular forces are responsible for solids & liquids.

  10. Intermolecular Forces • All molecules are attracted to each other. • Some molecules are strongly attracted & some are only weakly attracted. • If it wasn’t for intermolecular forces,everything would be a gas!!!

  11. What is a phase change? • A transition between phases. There are 6. What are they?

  12. Boiling or Vaporization source H2O(l)  H2O(g)

  13. H2O(s)  H2O(l) source source Melting or Fusion

  14. I2(g)  I2(s) Deposition I2(s)  I2(g) Sublimation source

  15. H2O(g)  H2O(l) Condensation source

  16. H2O(l)  H2O(s) Freezing source

  17. Chunk of dry ice in water. source

  18. Phase Changes • When a substance goes from the gas to a condensed phase, what happens? • The particles get closer together and their translational motion (movement from point A to point B) slows down. • We cool it and/or compress it.

  19. Gas to Liquid

  20. Phase Changes • When a substance goes from a solid to a liquid or a gas, what happens? • The particles move far apart and their translational motion increases. • We heat them up and/or reduce the pressure.

  21. Phase is determined by the competition between kinetic energy & intermolecular forces

  22. Kinetic Energy vs.Intermolecular Forces

  23. Kinetic Energy  Intermolecular Forces • Weak intermolecular forces: even with low K.E. the particles can “escape” from one another & move far apart. • Move the magnets past each other quickly. Can the magnet in your right hand feel the magnet in your left hand? • What phase has weak intermolecular forces? Gas phase

  24. Intermolecular Forces  Kinetic Energy • Strong intermolecular forces: the particles may be trapped next to each other unless they are moving fast. • Move the magnets past each other slowly. What happens? • What phase has strong intermolecular forces? Solid phase

  25. Solid Phase – strong intermolecular forces • The stronger the intermolecular forces, the higher the melting point & boiling point. • Gas Phase – weak intermolecular forces • The weaker the intermolecular forces, the lower the melting point & boiling point.

  26. Sublimation • What can you say about the intermolecular forces in I2? (I2 sublimates.) • They are pretty weak!

  27. Particle Diagram of I2 White lines represent forces of attraction between I2 molecules.

  28. Potential Energy of a Pure Substance • Equal quantities of ice & water at 0C have the same kinetic energy, although the molecules move differently in the 2 phases. • They have different potential energy. • The farther apart the particles, the greater the potential energy. • For potential energy, gases  liquids  solids.

  29. Potential vs. Kinetic Energy of H2O • How can I start with H2O at 0C and raise the temperature to 50C? • I have to add energy to the system and it increases the kinetic energy of the water molecules. They move faster.

  30. Potential vs. Kinetic Energy of H2O • How can I start with ice at 0C and convert it to water at 0C? • I have to add energy to the system and it increases the potential energy of the particles. They move father apart from one another.

  31. Gas Going Up the ladder = Endothermic Process Net gain in energy. Potential Energy of System Liquid Going Down the ladder = Exothermic Process Net loss in energy. Solid

  32. Gas Going Up the ladder… Endothermic Process (Net gain in energy ) Potential Energy of System Liquid Going Down the ladder… Exothermic Process (Net loss in energy ) Solid

  33. source

  34. source

  35. Q = mCgT Q = mClT Q = mHv Q = mCsT Q = mHf Temperature Time

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