the nature of solids by mike, marc & alex. a model for solids - atoms, ions or molecules are...
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THE NATURE OF SOLIDS
by Mike, Marc & Alex
A Model for Solids
- Atoms, Ions or molecules are packed tightly together
- dense and not easy to compress
- solids tend to vibrate about
fixed points, they don't flow
State of Aggregation
- when heating a solid, particles vibrate more rapidly → kinetic energy increases
- when the solid reached its melting point it turns into a liquid
- the vibration is strong enough to overcome the attractions that hold them together
- melting and freezing point is at the same temperature
http://www.youtube.com/watch?v=kMR5KbNZ7b8&feature=related
Crystal Structure
- in a Crystal particles are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice
- Shape of a crystal reflects the arrangement of particles within a solid
Melting Points of Solids
- The melting Point of crystals is determined by the type of bonding between particles
- ionic solids have a high melting point → strong forces hold them together
- molecular solids have a low melting point
- Not all solids Melt (Wood, Cane Sugar)
Crystal Systems
A crystal has sides, or faces
- Sides and faces are always the same for a given substance
- There are 7 groups that crystals are classified into (Cubic, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Hexagonal, Rhombohedral)
- Shape of crystal depends on arrangement of particles
- Smallest group within a crystal that retrains the geometric shape of crystal is known as a UNIT CELL
Allotropes Are two or more different molecular forms of the same
element in the same physical state
Only a few elements have allotropes
Non-Crystalline Solids
- Not all solids are crystalline; some are amorphous
- Amorphous solids lack an ordered internal structure
- Atoms are randomly arranged
- Glasses are one example for an amorphous Solid
- a glass is a transparent fusion of inorganic substances that have cooled to a rigid state without crystallizing.
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