Crystal System Terms Unit Cell smallest repeating unit of a crystal structure Slip Planes surface along which layers of atoms can slide past one another plane of closely packed atoms Crystal System Terms ID: 600820
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Slide1
Crystal SystemsSlide2
Crystal System Terms
Unit Cell
smallest repeating unit of a crystal structure
Slip Planes - surface along which layers of atoms can slide past one another
plane of closely packed atomsSlide3Slide4Slide5
Crystal System Terms
Void or Interstice-
empty space in a crystal Slide6
Crystal Packing – loosely packedSlide7
Crystal Packing – More Densely Packed
Most metals are
close packed
- that is, they fit as many atoms as possible into the available volumeSlide8Slide9
SIMPLE CUBIC
FACE CENTERED CUBIC
(FCC)
BODY CENTERED CUBIC
(BCC)
HEXAGONAL CLOSE PACKED
(HCP)Slide10
simple cubic
FCC
BCC
HCPSlide11
Slip Planes of FCC
Morton SchafferSlide12
Slip Planes
Morton Schaffer
1Slide13
Slip Planes
Morton Schaffer
2Slide14
Slip Planes
Morton Schaffer
3Slide15
Slip Planes
Morton Schaffer
4Slide16
Slip Planes
Morton Schaffer
5Slide17
Slip Planes
Morton Schaffer
6Slide18
Slip Planes
Morton Schaffer
7Slide19
Body-centered cubic (BCC)
Face-centered cubic (FCC)
Hexagonal close-packed (HCP)
center atom
Slip Planes
Morton Schaffer
12 Slip Planes
Up to 48 Slip Planes
3 Slip PlanesSlide20
Why do Crystal Systems Matter?
Workability
changing the shape of a solid without breaking or cracking
Malleability
ability of being hammered into thin sheets
Ductility
ability of being drawn into wiresSlide21
Workability
Which crystal structure is more workable?
Many slip planes or few slip planes?
Tightly
packed or loosely packed? Slide22
Models of Crystals Lab
*more tightly packed = more workable
*more slip planes = more workable
Type of crystal structure
Closely packed?
Many slip planes?
Workability
FCC
BCC
HCPSlide23
Models of Crystals Lab
*more tightly packed = more workable
*more slip planes = more workable
Type of crystal structure
Closely packed?
Many slip planes?
Workability
FCC
Yes
Yes
Highest
BCC
No
Yes
Medium
HCP
Yes
No
LowestSlide24
Crystal Structures & Metals
BCC
FCC
HCP
OtherSlide25
Crystal Structures & Metals
BCC
FCC
HCP
Other
Chromium
Aluminum
Cobalt
Manganese
Iron (<910°C)
Calcium
Magnesium
tin
Molybdenum
Copper
Titanium
Sodium
Gold
zinc
tungsten
Iron (>910°C)
Lead
Nickel
Platinum
silverSlide26
26
Sargent Welch Periodic Table
Crystal structures on the back.Slide27
Sulfur Lab
Growing CrystalsSlide28
Sulfur MSDSSlide29
Sulfur MSDSSlide30
Sulfur MSDSSlide31
Sulfur MSDSSlide32
Monday, 9/19/16
Review lab on Friday!Slide33
Part A – Rhombic Sulfur
Forming crystals from a solution
Heated in mineral oil to dissolve
Crystals formed in solution
Sketch and describeSlide34Slide35Slide36
Part B: Monoclinic Sulfur
Forming crystals from a melted substance
1
. Fill a test tube approximately
1/2
full with sulfur. Keep the sulfur powder off the sides of the test tube.
2. Make a cone out of
filter paper
and place it in a funnel. (Make a sketch.)Slide37Slide38
Part B: Monoclinic Sulfur
3. Heat the test tube of sulfur
very
slowly - passing it back and forth above the flame. Totally melt to a liquid. Use
Bunsen burner
and test tube clamp. Keep the sulfur
yellow
.
4. Pour liquid sulfur into filter paper cone. As soon as a
crust
forms, open the filter paper to original shape.Slide39Slide40
Part B: Monoclinic Sulfur
5. Make observations of crystals formed. Use stereoscope.
6. Clean up!!!!!Slide41Slide42Slide43Slide44
Part C: Amorphous Sulfur
Heat sulfur slowly. It will pass through stages:
melt to yellow liquid
red liquid
dark reddish-brown thick syrup
dark runny liquid
Pour hot sulfur into beaker of cold water. (quench
)
Like pouring maple syrupSlide45
Ring of 8
sulfur atoms
Chain of
sulfur atomsSlide46Slide47Slide48
melt to yellow liquid
individual rings of 8
red liquid
short chains of 8 – 16 sulfur atoms
dark reddish-brown thick syrup
longer chains of sulfur atoms that entangle
dark runny liquid
longer chains of sulfur atoms that have enough energy to flowSlide49
Amorphous SulfurSlide50
Crystalline balls
of sulfurSlide51
Crystalline vs. Amorphous?
Orderly arrangement
Repeating pattern
Predictable
Opaque (not see through)
Random arrangement
No repeating pattern
Not predictable
ClearSlide52
Allotropes
Different forms of the same element in the same physical state
Difference is in how the atoms are arranged
Also called polymorphism
Examples:
Carbon – diamond, graphite, buckyballs
Oxygen – O
2
(atmospheric) and O
3
(ozone)
Sulfur – rhombic, monoclinic, amorphousSlide53
Allotropes of Carbon
buckyballSlide54
Allotropes of Sulfur
rhombic
amorphous
monoclinicSlide55
Solid State Phase Change
Change in crystal structure while remaining a solid.
Example:
Amorphous sulfur changing to crystalline sulfurSlide56
Milk Jug Demo
What is happening when you heat the plastic to the crystal structure?