Compare the properties of solids, liquids and gases

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Learning outcomes

• Compare the properties of solids, liquids and
  gases
• Describe quantitatively the molecular structure
  of solids, liquids and gases, relating their
  properties to the forces and distances between
  molecules and to motion of molecules
• Describe the relationship between motion of
  molecules and temperature

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8.1 States of Matter

• Three states of matter
• Solid Liquid Gas
• For example, iceberg, sea water and steam

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8.1 States of Matter

• Properties of Solids, Liquids and Gases

Solid Liquid Gas
Fixed shape Fixed volume Fixed volume Does not have fixed shape Assumes shape of container No fixed shape No fixed volume Assumes the shape and volume of container
Not compressible Not easily compressible Highly compressible
Does not flow easily Flows easily Flows easily
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8.1 States of Matter

• Molecular Structure of Solids, Liquids and Gases
• Solids
• Distances between molecules
• Molecules arranged close together in regular
  pattern
• Incompressible because molecules are close
  together with little space between them

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Solids
• Forces between molecules
• Balanced forces between molecules hold them in
  fixed positions
• Molecules vibrate about fixed positions,
  alternately attracting and repelling one another
• Strong attractive forces prevent molecules from
  leaving fixed positions while repulsive forces
  between atoms prevent them from collapsing into
  one another.
• Attractive and repulsive forces explains why a
  solid has fixed shape and fixed volume.

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Solids
• Motion of the molecules
• When a solid is heated, molecules gain energy and
  vibrate more.
• Separation between molecules increase slightly
  and the solid expands.

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Liquid
• Distances between molecules
• Molecules not arranged in regular pattern
• Molecules slightly further apart than in solids
• Liquids cannot be easily compressed as molecules
  are close together with little space between
  them.

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Liquid
• Forces between molecules and motion of the
  molecules
• Molecules vibrate to and fro, alternately
  attracting and repelling one another.
• Molecules not held in fixed position by
  attractive forces.
• Molecules move among one another throughout the
  liquid.
• Explains why liquids flow and take the shape of
  container

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Liquid
• Forces between molecules and motion of the
  molecules
• Attractive forces between molecules make it
  difficult for molecules to leave the liquid.
• Thus liquids have fixed volume.
• When a liquid is heated, molecules vibrate and
  move about more vigorously.
• Thus liquid expands, but only very slightly.

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8.1 States of Matter
Molecular Structure of Solids, Liquids and Gases

• Gas
• Distances between molecules
• Molecules are far apart
• Mainly empty space between molecules
• That is why gas can be compressed easily.

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8.1 States of Matter

• Forces between molecules motion of molecules
• Molecules move randomly at high speed
• Intermolecular repulsive forces act only when
  molecules collide with one another and with the
  walls of container.
• Molecules are so far apart that intermolecular
  attractive forces are negligible in a gas.
• A gas is thus able to expand and fill a container
  completely.

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The three states of matter are solid, liquid and
gas.
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8.2 Kinetic Model

• The kinetic theory of matter states that all
  matter is made up of a large number of tiny atoms
  or molecules which are in continuous motion.
• Molecules are too small to be seen directly.
• Existence of particles in continuous motion has
  been demonstrated by Brownian motion and
  diffusion.

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8.2 Kinetic Model

• Motion of Molecules and Temperature
• When temperature increases, thermal energy of the
  molecules increases and the molecules move
  faster.
• The molecules gain kinetic energy.

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1. When the temperature increases, kinetic energy of
   the molecules also increases.

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