10.3: Solids By: Grace, Rosa, Zoie and Jaylen

Properties of Solids in Kinetic- Molecular Theory The particles of a solid are closely packed, therefore the intermolecular force between particles are far more effective in solids. There are 2 types of solids: crystalline and amorphous ( although, most solids are crystalline.)

Crystalline Solids Crystalline solids contain crystals A substance in which particles are arranged in an orderly,geometric, repeating pattern. Maintain definite shape and are geometrically regular. Even when shattered, the fragments have distinct geometric shapes that reflect internal structure. Melting point for Crystalline solids are definite. Particles can break out of their positions. Exist either as single crystals or groups fused together. The total 3-dimensional arrangement of particles in the crystal is called, crystal structure. In each crystal lattice, the smallest portion of the entire pattern id is called a unit cell.

Types of Crystalline Solids 1. Ionic Crystals- consists of positive and negative ions arranged in a regular pattern and can be monatomic or polyatomic. Form when Groups 1 or 2 metals combine with Groups 16 or 17 non metals or nonmetallic polyatomic ions. These crystals are hard and brittle with high melting points and are good insulators. 2. Covalent network crystals- each atom is covalently bonded to its nearest neighboring atoms. 3-dimensional covalent network solids include diamond, Cx, quartz, silicon carbide and many oxides of transition metals.Network solids are nearly always brittle and hard with rather high melting points and are usually nonconductors/semiconductors.

Types of Crystalline Solids Cont. 3.Metallic crystals- consists of metal cations surrounded by delocalized valence electrons. Electrons come from the metal atoms that belong to the crystal. The delocalized electrons move freely throughout the the crystal, which gives it the high electric conductivity of metals. 4.Covalent Molecular Crystals- consists of covalently bonded molecules bonded molecules held together by intermolecular forces. Covalent molecular crystals have low melting points, are easily vaporized, soft and are good insulators.

Amorphous Solids Particles are arranged randomly Solids such as glass and plastics are amorphous. Maintain definite shape, although do not have distinct geometric shapes of crystalline solids, the word amorphous comes from Greek meaning, “no shape”. I.e.: glass can be molded into any shape, but if shattered, fragments can have wide variety of shapes. Amorphous solids have no definite melting point. Have the ability to flow over range of temperatures, therefore can be classified as supercooled liquids(substances that retain certain liquid properties even at temperature at which they appear to be solid).

Practice questions 1. How are the particles packed in solids? A) loosely B) tightly C) randomly 2. Solids have a definite shape and volume… True or False 3. Solids have a high density… True or False