Presented by: Lee Liak Ghee 2i3 (10)
Introduction
What is solid? Fixed shape & volume Molecules closely packed, vibrates about fixed positions Strong intermolecular bonds What is liquid? Indefinite shape & fixed volume Molecules in clusters, slide over one another Weak intermolecular bonds
Solids Crystalline molecular structure Molecules vibrate about fixed positions Heat increases vibrations Melting point molecules start to flow lose crystalline structure Distinct phase transition melting/freezing involves heat of fusion
Liquids Viscosity: resistance to flow e.g. water 0.01 poise; thick oil 1.0 poise Cooling a liquid - increases viscosity Below melting point molecules form crystals and solidify Super-cooled liquid - remains liquid below freezing point Depends on nucleation sites
What is Non-newtonian?
What is Glass made of?
What is Glass Made of? 2 types: Natural Glass and Man-made Glass Natural Glass Formed when rocks melt Lightning Volcanic eruptions Amorphous structure High Silicon Dioxide(SiO 2 ) capacity Examples: Obsidian and Tektite
Natural Glasses ObsidianTektite
Man-made Glass Made of sand, soda ash & limestone Heated to a high temperature Cooled Transparent, non-crystalline material formed
Who and How was Glass Discovered?
Natural glass In use since the stone age Man-made glass In use as far back as 5000 years ago Discovered by the ancient Egyptians
Molecular Structure of Glass
Amorphous structure Long chain of atoms No crystalline structure
Characteristics of Glass
Amorphous solid Brittle Transparent
Glass: Solid or Liquid?
How Glass is Formed Supercooled liquid cools further Molecules remain disordered Develops rigidity Becomes amorphous solid e.g. amorphous ice forms at -137 °C Glass is formed in this manner
Glass is Liquid? Old glass panes thicker at the bottom than the top Some glass panes sagged Some have rippled surfaces Glass is a liquid with very high viscosity? Solid has viscosity ≥ poise Liquid has viscosity < poise
Proof: Glass does not flow Excellent images of telescope lenses Stone age arrow heads remain sharp Excellent condition of 1 st century A.D. Roman glassware Stone Age Arrow Head 1 st Century A.D. Roman Glassware
Conclusion
From our viewpoint glass is solid Scientific arguments are less conclusive
Non-newtonian Pool
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Acknowledgement ages/a/ar/arrowhead.jpg lated ITHJuTpQ&feature=related m/how_is_glass_made
The End