The Nature of Solids

Chapter 10

Solids:

• Gases = very free to move

• Liquids = relatively free to move

• Solids = not very free to move

Solids:

• Solids do not move freely like liquids and gases

• Rather, they vibrate about fixed points

Solids:

• Do not take the shape or volume of the container

• They are dense and incompressible

Solids and kinetic energy:

• Increase in average kinetic energy = increase in particle vibration = increase in temperature

Melting Point:

• Mp = Solid turning to liquid

• Vibrations are strong enough to overcome the intermolecular interactions

Freezing Point:

• Opposite of melting point

• Liquid turns into a solid because the particles slow down and intermolecular forces are stronger

Equilibrium:

• A solid will melt and freeze at the same temperature

• This is the point of equilibrium, assuming temperature is remaining constant

Solids:

• Ionic Solids (ex: NaCl) = high melting points

• They have relatively strong forces holding them together

This is table salt

Solids:

• Molecular compounds = low melting temperatures

• Example – hydrogen chloride has a melting temperature of -112 0C

Solids:

• Not all solids melt, some will decompose

• Example: wood, cane sugar

Sugar or RockCandy

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Crystal structure:

• Crystalline (crystals) = atoms, ions or molecules are arranged in a repeated, three dimensional pattern called a crystal lattice

Crystals:

DiamondStructure

Crystals:• Have regular shape• Shape reflects the arrangement

of the particles within the solid• Types of bonds determines the

melting point• Ionic = high melting point• Molecular = low melting point

Graphite Structure

Crystals:

• Have sides or faces

• Angles of the sides for a given crystal are always the same

Crystal Classification:

• Galena–Cubic

Crystal Classification:

• Zircon–Tetragonal

Crystal Classification:

• Blue Topaz–Orthorhombic

Crystal Classification:

• Gypsum–Monoclinic

Crystal Classification:

• Amazonite–Triclinic

Crystal Classification:

• Tourmaline–Hexagonal

Crystal Classification:

• Calcite–Rhombohedral

Shape of Crystals:

• Shape depends on arrangement of crystals

• Unit cell = smallest group of particles that retains geometric shape

More than one Form?

• Carbon is an example of a crystal that can exist in more than one form

Many forms of carbon:

• Diamonds• Graphite• Buckyball or

Buckminsterfullerene- 60 + carbon atoms shaped like a soccer ball

Many forms of Carbon:

• Allotropes–Two or more molecular forms of

the same element in the same physical state (diamond, graphite & buckyballs)

Example: diamonds and graphite

Amorphous Solids:

• Lack ordered internal structure• Non- crystalline• Example- rubber, plastics,

asphalt and glasses–Glasses are sometimes called

super cooled liquids

Now, go on to the Nature of Nature of LiquidsLiquids Power Point

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Nature of LiquidsNature of Liquids