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Crystals - PowerPoint PPT Presentation

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Crystals. I. Crystals. Rigid bodies in which the particles are arranged in units that form a repeating pattern. This particle arrangement gives the crystal a definite shape. . A. True Solids. All true solid substances are crystalline They have a definite melting point

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PowerPoint Slideshow about 'Crystals' - Patman

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i crystals
I. Crystals
  • Rigid bodies in which the particles are arranged in units that form a repeating pattern.
  • This particle arrangement gives the crystal a definite shape.
a true solids
A. True Solids
  • All true solid substances are crystalline
  • They have a definite melting point
  • They have flat faces with definite angles
  • Crystalline solids "cleave" along unit cell lines

b amorphous solids
B. Amorphous Solids
  • Non-crystalline solids
  • Amorphous substances do not have a pattern when they break.

Shattered Glass

Amorphous Carbon

c steno s law
C. Steno’s Law
  • All crystals of a substance have the same angle between their faces
  • An INTRINSIC (or intensive) property—does not depend on amount, size, etc.
nicolaus steno 1699
Nicolaus Steno—1699
  • Discovered Steno’s duct; a duct of the salivary gland
  • Steno's law of superposition: layers of rock are arranged with the oldest on the bottom and the youngest on the top
  • Was ordained as a Roman Catholic priest in 1675
d forces holding crystals together
D. Forces Holding Crystals Together
  • Hydrogen Bonds ex: Ice
  • Van der Waals Forces ex: Sugar
  • Ionic Bonds ex: NaCl, CaCl2
  • Metallic Bonds ex: Fe, Cu, Al
e unit cells
E. Unit Cells
  • The simplest repeating unit in a crystal
  • The arrangement of these units is determined by the bond angle between the particles.
  • Crystals are made up of repeating unit cells
  • Ex: small & large diamonds have the same shape


Salt magnified 40 times

sample unit cells
Sample Unit Cells

Simple Cubic

Body Centered Cubic

Face Centered Cubic

f space lattice
F. Space Lattice
  • Three-dimensional arrangement of unit cells repeated over and over giving a crystal its overall geometric shape

a. Solute – the substance dissolved in a given solution

b. Solvent – a substance that dissolves another to form a solution.

  • Water is a solvent for sugar

c. Saturated solution - a solution obtained when a solvent (liquid) can dissolve no more of a solute (usually a solid) at a particular temperature

d. Unsaturated solution - a solution in which more solute can be dissolved

e. Supersaturated solution - a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances

f seed crystal



Sugar crystals

f. Seed Crystal

Seed crystal = the initial crystal

  • With rock candy, need a small sugar crystal to get large candies
  • With fudge, seed crystals lead to large crystal growth and bad, grainy fudge.

ii vocabulary continued
II. Vocabulary (continued)

h. Hydrated Crystals - Water molecules become chemically bonded to ions in the crystal.

  • Anhydrous Crystals Crystal without water

CuSO4• 5 H2Oa hydrated crystal

Farmers will truck anhydrous ammonia to save the cost of trucking the weight of the water in a hydrated crystal.
j. Desiccant - Anhydrous substances that gain water so easily that they can be used to remove water from other substances.

ex: Silica gel packets found in new shoes…

k. Hygroscopic - a solid whose ions capture water molecules out of the air

l. Deliquescent - a solid so strongly hygroscopic that it slowly dissolves in air

m. Viscosity - the property of a fluid that resists the force tending to cause the fluid to flow. (how “sticky” a liquid is)
iii dissociation review
III. Dissociation Review

Na+ (aq) + Cl-(aq)

NaCl(s) 

___ moles of solute

CaBr2 (s) 

___ moles of solute

Mg3(PO4)2 (s) 

___ moles of solute

C6H12O6 (s) 

___ moles of solute


Ca+2 (aq) + 2 Br-1 (aq)



3 Mg+2 (aq) + 2PO4-3 (aq)


C6H12O6 (aq)



iv freezing pt depression boiling pt elevation
IV. Freezing Pt Depression & Boiling Pt Elevation


1 mole of solute per liter of water lowers the freezing point by


Increases the boiling point by

1.86o C

0.51o C

b why do solutes reduce the freezing point
b. Why do solutes reduce the freezing point?
  • solute interferes with formation of space lattice.
c why do solutes increase the boiling point
P atm

t = 1 min

c. Why do solutes increase the boiling point?
  • solute lowers the vapor pressure, harder to boil.



20.00 g of MgCl2 is dissolved in 100 ml of water. What is the change in boiling & freezing points?

MgCl2 Mg+2+ 2 Cl-1

# solute particles?


0.21 mol MgCl2 x 3 mol solute =

0.63 mol of solute particles in 100 ml water

real life examples
Real Life Examples
  • Why do we use salt on roads?
    • To decrease the freezing point
  • Which is better, NaCl or CaCl2?
    • CaCl2 3 particles of solute
  • Is sugar a good de-icer?
    • NO! Only 1 particle of solute
why use antifreeze in your car
Why use antifreeze in your car?
  • To keep water in radiator from freezing
  • Freezing water will crack radiatorIce expands as it freezes
  • To keep water in radiator from boiling
Homemade ice cream
    • You add salt to the ice to decrease its temperature allowing the cream to freeze more easily, quickly with fewer large crystals  grainy ice cream
fp bp quiz
FP/BP Quiz

5.0 g Na2SO4 is dissolved in 100 ml of water.

1) Calculate the grams of Na2SO4 in 1000 ml H2O

2) Calculate the moles of Na2SO4 in 1000 ml H2O

3) Write the dissociation equation and determine the moles of solute in 1000 ml H2O

Na2SO4 2Na+ + SO42-

0.35 mol  1.05 mol solute

4) Calculate DTFP (Freezing Point Depression)

5) Calculate the new Boiling Point

antifreeze sample problem
Antifreeze Sample Problem

A sample of antifreeze contains 100 mol of ethylene glycol (covalent) in 5 L of water. Calc the FP & BP.

  • FP
  • BP

New freezing point?

-37.2 oC (-35oF)

New boiling point?

110.2 oC (230oF)

ice cream sample problem
Ice Cream Sample Problem

What mass of rock salt is needed in 1 L of water to lower the freezing point to -10oC?

Freezing Point depression?

How many moles of solute are needed?

Dissociation Eqn? How many moles of NaCl? grams?

NaCl  Na+ + Cl-



5.4 moles solute

2.7 moles

v hydrated crystals
V. Hydrated Crystals
  • Ex:

CuSO4 • 5H2O + heat CuSO4 + 5 H2O

(Blue) (White)




Hydrates – crystals with water
  • Anhydrous – crystal with no water
  • Water of Hydration:

1) The amount of water in a crystal

2) Water of hydration is a definite ratio

FeSO4  3 H2O

MW = __________

55.8 + 32.1 + 4(16.0) + 3 (18) = 189.9 g/mol

  • 1 H2O monohydrate
  • 2 H2O dihydrate
  • 3 H2O trihydrate
  • 4 H2O tetrahydrate
  • 5 H2O pentahydrate
  • 6 H2O hexahydrate
  • 7 H2O heptahydrate
  • 8 H2O octahydrate
  • 9 H2O nonahydrate
  • 10 H2O decahydrate
problem solving
Problem Solving

1) Find the % H2O in Sodium Sulfide trihydrate.

Na2S • 3H2O

problem solving38
Problem Solving

2) If 10 grams of Na2S  3 H2O is heated ______ grams of water will be lost. (40.9% water)

3) 1 mole of Na2S combines with ___ moles of H2O?

0.409 x 10.0 = 4.09 g of water lost


Na2S • 3H2O

The ratio is 1 to 3

problem solving39
Problem Solving

4) If 0.03 moles of CuSO4 is combined with 0.15 moles water, what is the formula? name?

5) If 0.04 mol of BeCl2 is combined with 0.08 mol water, what is the formula?

The ratio is 1 to 5

CuSO4• 5H2O

Copper (II) sulfate pentahydrate

The ratio is 1 to 2

BeCl2• 2H2O

Beryllium chloride dihydrate

problem solving40
Problem Solving

3.94 g CuCl2

i. mass of anhydrous crystal?

ii. moles of anhydrous crystal?

iii. moles of water?

iv. experimental mole ratio

v. formula of hydrated crystal?

vi. name of hydrated crystal?

6) Five grams of hydrated CuCl2 crystals lose 1.06 g of water when heated.

1 to 2 ratio

CuCl2• 2H2O

Copper (II) chloride dihydrate

vii allotropes
VII. Allotropes
  • Any of several crystalline forms of a chemical element. Ex. Charcoal, graphite, and diamond are all allotropes of carbon
  • S8 2 crystalline forms: rhombic & monoclinic
  • Sx 1 amorphous form: brown, plastic sulfur
      • Formed by rapid cooling
      • Will crystallize over time
White phosphorous shellsPhosphorous

White Phosphorous Video (skip to the middle)

  • Graphite – 2 dimensional bonding
      • VdW's forces between layers
      • brittle, breaks in layers
  • Diamond – 3 dimensional bonding
      • Hard and Durable
  • Fullerenes – C60 C70
eight common allotropes of carbon
Eight common allotropes of carbon



Bucky ball


What is the difference in bonding between Graphite and Diamond?
  • Three dimensional bonding in diamond, only two dimensional in graphite
  • O2 “normal” oxygen in the air we breathe.
  • O “nascent oxygen” –very reactive
  • O3 ozone— A thin layer in the upper atmosphere’ reflects UV light back into space.
ozone the good the bad the ugly
Ozone: The Good, The Bad, & the Ugly
  • Good: protects us from harmful UV rays
  • By banning CFC’s that destroy atmospheric ozone we’ve decreased the holes in the ozone layer.
ozone action days
“Ozone action days”
  • Weather conditions are favorable for ground-level ozone (smog) to reach unhealthy levels within our region, and your voluntary actions are requested. Please help and make a difference on this OZONE ACTION DAY by doing any of the following:
  • Car pool or use mass transit when possible
  • Bike to work
  • Refuel automobiles later in the evening
  • Postpone lawn mowing until the evening
  • Postpone using paints, lacquers and solvents until late in the afternoon
  • Reduce or postpone, when possible, industrial processing activities which produce VOC emissions
  • Reduce your demand for electricity