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Theory of Matter

How matter — anything that occupies space and has mass — is built of atoms and molecules, and how the kinetic molecular theory explains changes of state.

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What this chapter covers

  1. Matter and Molecular Motion

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    • Matter DefinitionOccupies space and has mass.
    • Atoms and MoleculesAtoms join together into molecules.
    • Intermolecular ForcesForces that hold molecules together.
    • Intermolecular SpaceGaps between molecules; largest in gases.
    • Molecular MotionMolecules in continuous, restrained motion.
    • Temperature and MotionHigher temperature raises average kinetic energy.
    • Kinetic TheoryMolecules move, restrained by attraction.

  2. Structure of Matter

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    • States of MatterSolids, liquids and gases compared.
    • Key DefinitionsAtom and molecule as smallest particles.

  3. Change of State Based on the Kinetic Molecular Theory

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    • Kinetic Molecular ModelTiny particles in constant motion.
    • Melting and FreezingParticles vibrate faster, then slide apart.
    • Boiling and EvaporationEnergetic molecules escape as vapour.
    • CondensationCooled gas particles lose energy.
    • Sublimation and DepositionSolid to gas directly; iodine, camphor.

  4. Law of Conservation of Mass

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    • The LawMass neither created nor destroyed.
    • Conservation in Chemical ReactionsAtoms rearrange; totals stay the same.

Try a sample question

The only type of motion allowed to the molecules of a solid is:

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