Matter

What this chapter covers

1. Composition of Matter

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   • MatterOccupies space and has mass.
   • MoleculesSmallest independent particle showing all properties.

2. Characteristics of Molecules

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   • SizeVery small, invisible under ordinary microscope.
   • Inter-molecular SpaceGaps between molecules; largest in gases.
   • MotionConstant random motion with kinetic energy.
   • Inter-molecular ForceElectrostatic attraction between molecules, short-range.
   • Cohesion and AdhesionAttraction within same versus different substances.

3. Molecular Model of Solids

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   • Inter-molecular SpacingVery close, packed tightly together.
   • Molecular MotionVibrate about fixed positions only.
   • Molecular ForcesVery strong; hold shape and volume.
   • Molecular ArrangementFixed positions, closely packed molecules.

4. Molecular Model of Liquids

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   • Inter-molecular SpacingMore spacing than in solids.
   • Molecular MotionMove freely within the container.
   • Molecular ForcesWeaker; keep volume, not shape.
   • Molecular ArrangementLoosely packed, no fixed positions.

5. Molecular Model of Gases

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   • Inter-molecular SpacingVery large; molecules far apart.
   • Molecular MotionMove freely in all directions.
   • Molecular ForcesNegligible inter-molecular force of attraction.
   • Molecular ArrangementRandom arrangement; no fixed shape, volume.

6. Distinction Between Solids, Liquids and Gases

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   • Shape and VolumeSolid both fixed; gas neither fixed.
   • Molecular RigiditySolids rigid; liquids and gases non-rigid.
   • Molecular MotionVibrate, move within boundary, or everywhere.
   • Positional FixityOnly solid molecules stay in place.
   • Inter-molecular ForcesStrongest in solids, weakest in gases.
   • Molecular PackingClose in solids, far in gases.
   • FlowLiquids and gases flow; solids cannot.

7. Change of State

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   • OverviewAbsorbing or rejecting heat changes state.
   • Solid-Liquid TransitionsMelting or fusion, and freezing.
   • Liquid-Gas TransitionsBoiling, and condensation back to liquid.
   • Solid-Gas TransitionsSublimation, and deposition back to solid.

8. Melting

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   • MeltingSolid to liquid at melting point.
   • Molecular ExplanationLatent heat increases molecular separation.

9. Freezing

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   • Freezing PointLiquid solidifies at its freezing point.

10. Vaporization or Boiling

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    • VaporizationLiquid to gas at boiling point.
    • CondensationGas to liquid on cooling.
    • Molecular ExplanationLatent heat lets molecules break free.

11. Evaporation

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    • EvaporationLiquid to gas at any temperature.
    • Rate of EvaporationFaster with temperature and surface area.
    • Evaporation and CoolingTakes heat from surroundings, cooling them.
    • ApplicationsEarthen pot cools water; fever cloth.
    • Molecular ExplanationEnergetic molecules escape from the surface.

12. Sublimation and Deposition (or Solidification)

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    • Sublimation and DepositionSolid to gas directly, and back.
    • Molecular ExplanationWeak forces let molecules change directly.

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