Kinetic Theory of Solids Day 5 - Notes Unit: States of Matter Kinetic Theory of Solids Starting from upper left and moving across: Bucky ball, calcite, galena, zircon, glass, gypsum, topaz, amazonite, tourmaline

After today you will be able to… Describe solids according to the Kinetic Theory Explain differences and similarities between ionic and molecular solids

Kinetic Theory of Solids In the solid state, the particles have the lowest amount of KE. The IM forces in the solid state are higher than the IM forces in a liquid or gas. The particles in the solid state are in fixed positions. The particles vibrate in place and do not flow.

Two Types of Solids: Crystalline: Solids that contain particles that are arranged in an orderly, repeating pattern. Example: Table salt, NaCl Amorphous: lacks order among the particles that make it up. Example: Glass, SiO2 Amorphous solids are made by cooling a liquid rapidly so that the atoms/molecules do not have time to align themselves.

Amorphous Solid: Glass Crystalline Solid: Table Salt

Types of Crystalline and Amorphous Solids Ionic: (Metal and Nonmetal) the attraction of positive and negative increases the likelihood to stay in the solid state. Are always crystalline solids. The strong IM forces make it difficult to break apart.

Types of Crystalline and Amorphous Solids Molecular: (Nonmetals only) Held together by strong covalent bonds, but have much weaker IM forces. The IM forces for ionic solids are much stronger than in molecular solids. Can be amorphous or crystalline.

Phase Changes for Solids A solid will melt when the particles in the solid state have enough KE to break free from their fixed positions. The temperature at which this occurs is called the melting point (m.p.). Since IM forces are stronger in ionic solids, they will have higher m.p.s than molecular solids.

Phase Changes for Solids Sublimation: the conversion of a solid to a gas without going through the liquid state. The reverse process is called deposition.

Phase Changes for Solids Sublimation occurs when the vapor pressure of the solid is greater than or equal to the surrounding atmospheric pressure. Vapor Pressure ≥ Atm Pressure

The vapor pressure of solids is usually much lower than the VP of liquids. VP will increase if the solid is heated. However, most substances will melt before the vapor pressure = atm pressure. (This is why sublimation is so difficult.) It is easier to get a solid to sublime by lowering atmospheric pressure. Dry ice sublimes at room temperature and pressure because it has a high vapor pressure due to its weak IM forces.

Questions? Complete WS 5