WebLecture: Lattices and Phase Changes
Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 12: Sections 4-7.
- 12.4 Band theory is used ot explain high melting points, delocalized bonding between atoms, and conductivity in metals. Since more orbitals are available than there are electrons to fill them, electrons can move relatively easily from one energy level to another and from one atom to another. These bands are not completely continuous, however, and the energy required to make jumps between them explaines the behavior of semiconductors, which underlies modern electronics and computer technologies.
- 12.5 Other kinds of solids: Molecular, Network, and Amorphous: Molecules tend to form solids based on their dispersion forces. Network solids are hard, rigid, three dimensional arrays of covalently bonded atoms. As with ions, these are extensions of atomic arrays, not molecules. Similarly, amorphous solids are collections of atoms, but their organization is irregular, with long and short bonds. As a result, amorphous solids melt slowly over a range of temperatures.
- 12.6 Phase Changes Involving Solids: The enthalpy of fusion is the amount of heat absorbed as a solid changes to a liquid state. The enthalpy of crystallization is the amount of heat given off or "evolved" when a substance freezes. For a given substance the enthalpy of fusion is equal to the enthalpy of crystallization, the only difference is the direction of heat flow.
- 12.7 Phase Diagrams: One common way to represent how solid, liquid, and gas states can co-exist is to use a phase diagram plotting the state as a function of pressure and temperature. The shape of the curve and the slope of the interface between solid and liquid states reflect the density propeerties of the substance. Because water is denser in the liqud state than inthe solid state, its liquid-solid equilibrium line has a negative slope.
Videos for Chapter 12: The Solid State
Review the Videos at Thinkwell Video Lessons.
- Under "Chemistry of Metals"
- An Introduction to Metals
Band Theory of Conductivity
- Intrinsic Semiconductors
- Doped Semiconductors
Homework problems: See your Moodle assignment!
AP #9 GUIDED INQUIRY — Measuring the dependence of reaction rates on temperature, surface area, concentration, and catalysts -- Phase III
Write your formal report on this experiment. Be sure to include any graphs of data and error analysis that you performed.
- AP2009 12 Determination of the Rate of a reaction and its order
- APGIE Investigation 10 Kinetics: Rate of Reaction: How Long Will that Marble Statue Last?
- IGHCE Lab 12.1-4 Determination of the effect of Temperature, Surface Area, and Catalysts on Reaction Rates
- IGHCE Lab 12.2 Determination of the effect of Surface Area on Reaction Rate
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