1. Growing Crystals Background and Sulfur Lab

2. Crystal -Review
Definition: group of atoms that form a particular repeating pattern
Today we will try to grow some crystals and observe the properties.

3. Crystal Definitions Grains Grain Boundary
individual crystals in a solid
start growing in different places and meet up
Grain Boundary
where grains meet up in a solid
smaller crystals have more grain boundaries
affect physical properties
A grain is merely a crystal without smooth faces because its growth was impeded by contact with another grain or a boundary surface.

4. Crystal Definitions Dendrites crystal branches
crystal growth pattern – directional
grow until they eventually become large enough to impinge upon (interfere with) each other
spaces between the dendrite arms
crystallize to make a more regular
crystal

5. Once nucleated, the dendrites spread sideways and the secondary arms generate further tertiary arms and so on. When solidification is complete, all the dendrites that have formed knit together to form grains (or crystals).

6. Snow - Ice
Snow - ice

7. Dendritic copper crystals

8. Ways to form Crystals Solutions
Cooling a liquid from a melt (freezing)
Grow as a precipitate from a chemical reaction
From a solution as the solvent cools or evaporates
Solutions
Solution: homogeneous mixture
involves dissolving, physical process
Solute: material that gets dissolved
Solvent: material that does the dissolving
Example: Sugar dissolving in water

9. Types of Solutions unsaturated saturated supersaturated
can hold (dissolve) more solute
saturated
no more solute can dissolve at that particular temperature
supersaturated
more solute is dissolved than it can normally hold at a particular temp
heat it, then cool it

10. Growing Crystals – Sulfur MSDS

11. Sulfur MSDS
Safety Notice: The ignition temperature of sulfur here is very low - FIRE HAZARD!
Have wet towels available to smother the flame.
Take care not to burn hands!
Sulfur Dioxide is toxic. Dispose of in trash can.

12. Growing Sulfur Crystals Lab
Three methods of growing crystals.
Students: Follow directions in lab worksheet on how to perform.
TAKE Safety precautions!!!!!
Leave this slide here until lab is finished – lab may take whole period.

13. Journal List your lab partners.
Problems and successes in lab technique – Part B.
Do you observe differences in the different crystals formed by the different methods?

14. Background on Sulfur Sulfur Electron Configuration:
1s2 2s2p6 3s2p4
Can acquire two electrons or donate e-
Sulfur Molecule – S8
Sulfur is nonpolar
Does not dissolve in water!
Only in nonpolar solvents

15. Structures of Sulfur
Chain of
sulfur atoms
Ring of 8
sulfur atoms

16. Sulfur Structures Observed
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 flow

17. Solid State Phase Change
Change in crystal structure while remaining a solid
Example: Allotropes
Amorphous sulfur changing to crystalline sulfur
What other elements have allotropes?

18. 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 – O2 (atmospheric) and O3 (ozone)
Iron – BCC to FCC transition at high temperatures

19. Allotropes of Sulfur Sulfur forms more than 30 types of allotropes!
rhombic
amorphous
monoclinic

20. Allotropes of Carbon buckyball
Great web page about crystals

21. Supplementary Slides

22. Crystalline balls
of sulfur