Types and Properties of Solids.pdf

TYPES AND PROPERTIES OF SOLIDS WHAT IS SOLID? SOLID -defined as that form of matter which possesses rigidity and hence possesses a definite shape and a definite volume -They can only vibrate about their fixed position. Therefore, solids are rigid and have...

TYPES AND PROPERTIES OF SOLIDS WHAT IS SOLID? SOLID -defined as that form of matter which possesses rigidity and hence possesses a definite shape and a definite volume -They can only vibrate about their fixed position. Therefore, solids are rigid and have definite shape.  GENERAL CHARACTERISTIC OF SOLIDS 2 main properties: They have strong intermolecular forces and short internuclear distance due to close packing of constituent particles. Their constituent particles don’t possess translator motion but can oscillate only around their mean position. Due to these two basic properties, solids possess the following characteristic properties. They have definite shape, mass and volume. They are rigid and incompressible. They have high density.  TYPES OF SOLIDS A. Crystalline Solids - All solid metals, nonmetals and compounds come in this category. B. Amorphous Solids - Rubber, glass, pitch, polymers of high molecular mass, quartz glass, etc., are the examples of it.  MAIN PROPERTIES OF SOLID Arrangement of constituents particles In a crystalline solid, the particles (ion, molecule or atoms) are arranged in definite geometric pattern in the three dimensional network. Melting point Anisotropy-In a crystalline solid, the properties like electrical conductance, refractive index, thermal expansion, etc., Clean Cleavage with knife-A crystalline solid gives a clean surface after cleaving it with a knife rather than an irregular breakage.  CRYSTALLINE SO LIDS THESE ARE THE SUBSTANCES WHOSE CONSTITUENT PARTICLES POSSESS A REGULAR ORDERLY ARRANGEMENT. THEY ARE CONSIDERED AS TRUE SOLIDS. FOR EXAMPLE, NACL (ROCK SALT), SUCROSE (SUGAR), DIAMOND, QUARTZ, ETC.  CLASSIFICATION: Ionic solid Molecular Solids Covalent or Network Solids Metallic Solids IONIC PROPERTIES Ionic crystals are brittle The crystal lattice structure of an ionic crystal is held together by the attraction of oppositely charged ions. If the crystal is struck with a hammer, the ions become distorted and they repel one another causing the crystal to break or shatter. Hard High melting points soluble in water conduct electricity but only in solution or in the liquid state METALILIC CRYSALS are solids with closely packed atoms held together by electrostatic interactions and free moving electrons. Electron Sea Theory- is a theory that states that the electrons in a metallic crystal move freely around the positively charged nuclei Metallic Bonding-is the bonding that holds the nuclei and electrons of metals together PROPERTIES: Metals have a low ionization energy and easily give up electrons The metallic ions pack together as closely as possible and are held in place because of strong electrostatic forces between the ions and the delocalized electrons Melting points vary widely Sheen-Mobile valence electrons absorb and emit light energy of many wavelengths of light  Malleability-The “electron sea” allows atoms to slide over each other Electrical conductivity-Mobile valence electrons produce an electric current when a metal is connected to a battery Hardness-The “electron sea” surrounding the positive nuclei produces strong electrostatic attractions that hold the nuclei together MOLECULAR CRYSTALS Properties : Low melting point ( due to intermolecular interactions ) Little hardness (due to intermolecular interactions ) Electrical non-conductor ( composed of neutral molecules ) COVALENT NETWORK CRYSTALS is a solid in which the atoms form covalent bonds in an interwoven network. ex: quartz crystal Properties: Very high melting points Extreme hardness Not good conductors of electricity AMORPHOUS SOLIDS- substances whose constituent particles don't possess a regular orderly arrangement Amorphous solids glass and plastics are very useful materials and are widely used in construction, house ware, laboratory ware, etc. Amorphous silica is one of the best materials for converting sunlight into electricity (photovoltaic). Amorphous solid rubber is used in making tires, shoe soles etc.