Crystals, Ions and Solutions

1
Crystals, Ions and Solutions

• Chapter 10
• Carmen Alex

2
Crystals, Ions and Solutions

• How do atoms bond into a solid?
• Why do metals conduct electricity?
• Why do some substances dissolve in water?
• Why do other substances only dissolve in alcohol?

3
Crystals, Ions and Solutions

• Crystalline solids
• Specific melting temperature
• Quartz
• Snowflakes
• Asbestos
• Mica
• Amorphous solids
• Gradual melting
• Glass
• Pitch
• Plastics

4
(No Transcript)
5
Crystalline Solids

• Four classes of crystalline solids
• Types of bonding
• Ionic
• Covalent
• Metallic
• Molecular

6
10.1 Ionic and Covalent Crystals

• Ionic bonding (electron transfer) happens when
  metals interact with nonmetals
• Ionic bonds
• Are fairly strong
• Result in hard crystals
• Have high melting points

7
10.1 Ionic and Covalent Crystals

• Covalent bonding (electron sharing)
• Covalent bonds
• Are not soluble in water
• Do not conduct electricity

8
10.1 Ionic and Covalent Crystals

• Carbon bonds
• Diamond
• Each carbon atom has four nearest neighbors
• The atoms are held together by covalent bonds
• Melts at 3500C
• Graphite
• Each atom is linked to three others in sheets
• The sheets are held together by van der Waals
  forces
• Becomes a gas when heated to 3000C

9
10.2 Metallic Bonds

• Metal atoms have loosely attached outer (valence)
  electrons
• Metal molecules share a sea of outer electrons
• The free electrons can move about easily and
  therefore are good conductors for
• Heat
• Electricity

10
10.3 Molecular CrystalsVan der Waals Forces

• Polar covalent bonds (i.e. H2O) behave as if one
  end was positively charged, the other end
  negatively
• Nonpolar molecules charges can fluctuate in a
  way that they become attracted to each other just
  like with polar bonds

11
(No Transcript)
12
10.4 Solubility

• Solutions contain (at least) two substances
• Solvent gt Solute
• Concentration Solute per solvent
• Solutions (like compounds) are homogenous
• Solutions (unlike compounds) do not have fixed
  compositions

13
10.4 Solubility

• Saturated solutions contain the maximum amount of
  solute
• Solubility
• of solids increases with temperature
• of gases decreases with temperature
• but increases with pressure
• Solutions usually have
• Higher boiling points
• Lower freezing points (than the solvent itself)

14
10.5 Polar and Nonpolar Liquids

• Like dissolves Like
• Water dissolves salt and sugar
• Gasoline dissolves fats and oils
• If mixing polar and nonpolar molecules, the polar
  molecules will gather together and separate
  themselves from the nonpolar molecules.
• i.e. oil and water

15
10.5 Polar and Nonpolar Liquids

• Detergents are negatively charged on one end and
  nonpolar at the other. Thus they cling to
  nonpolar dirt while moving freely in water.
• Dissociation occurs when compounds dissolve into
  ions.
• i.e. salt in water

16
10.8 Water

• Origin
• Rocks
• Meteorites
• Volcanic gases
• Comets
• Avg. Composition
• 3.5 Salt
• 96.5 H2O

17
10.8 Water

• Type
• 3 fresh water
• 2 glaciers
• 1 liquid (rivers, lakes, aquifers, etc.)
• .5 industrial usage
• 97