8-3 Nature of Solids•General properties of a solid reflect the orderly arrangement of their particles and the fixed locations of their particles

--particles tightly packed

--dense, not easily compressed--vibrating particles around fixed points do not allow solids

to flow•Heating solids give the particles more KE, which in turn, causes the structure of the solid to break down, and eventually melt.

--Melting Point (mp) – point at which a solid begins to turn into a liquid.

--Why melting?

Because the increased vibrations are big enough that they overcome the strong attraction which holds them in a fixed place

Solidmelting

liquid

freezing

•Crystal structure

--most solids are crystals (orderly, repeating 3-D pattern called a crystal lattice)

--the shape of the crystal reflects the arrangement of the particles within the solid.

--bonding type between particles is what determines the melting points.

ionic bonding = high mp because strong forces

molecular bonding = low mp because weak forces

•Crystal systems

--have sides (faces)angles of where the faces intersect are always the same for a specific substance

--7 classifications (differ because of angles and number of edges of equal length on each face)

1. Cubic – galena

2. Tetragonal – zircon

3. Orthorhombic – topaz

4. Monoclinic – gypsum

5. Triclinic – amazonite

6. Hexagonal – tourmaline

7. Rhombohedral - calcite

•Unit Cell = smallest group of particles with a crystal that retains the geometric shape of the crystal

--14 kinds

•Allotropes – 2 or more different molecular forms of the same element in the same physical state

--some solid substances exist in more than one form

Carbon = exists as diamonds, graphite, buckyball

--allotropes have different properties because their structures are different

--only some elements have allotropes (phosphorus, sulfur, oxygen, boron, and antimony

•Amorphous solids = lacks orderly inside structure; non cryslalline

--random arrangement of the atomsrubber, plastics, asphalt, glass