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Discover the fascinating world of crystal formation through this crystal-growing experiment with sulfur. Learn the definitions of key crystal terms like grains, grain boundaries, and dendrites. Explore different methods of crystal formation, including cooling a liquid and using chemical reactions. Follow lab safety precautions while growing sulfur crystals and document your observations and findings. Gain insights into the structures and phases of sulfur, including its allotropes. Delve into the world of crystals and chemical structures with this engaging experiment.
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Crystal -Review • Definition: group of atoms that form a particular repeating pattern • Today we will try to grow some crystals and observe the properties.
Crystal Definitions • Grains • 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
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
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).
Ways to form Crystals • 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
Types of Solutions • unsaturated • 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
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.
Growing Sulfur Crystals Lab • Three methods of growing crystals. • Students: Follow directions in lab worksheet on how to perform. • TAKE Safety precautions!!!!!
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?
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
Structures of Sulfur Chain of sulfur atoms Ring of 8 sulfur atoms
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
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?
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
Allotropes of Sulfur • Sulfur forms more than 30 types of allotropes! monoclinic rhombic amorphous
Allotropes of Carbon buckyball
Crystalline balls of sulfur
