Main Ideas and Big Picture of CH304k_2 1up

Main Ideas and Big Picture of CH304k_2 1up - Walker CH304k...

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Walker CH304k Big Picture, Review, and Reference Materials Page 1 of 10 Main Ideas and Big Picture of CH304k Everything we know to exist is either matter or energy. Matter has mass and takes up space. Energy has no mass and does not occupy space as we know it. Matter can change forms; these changes are known as reactions. When matter changes form in an ordinary reaction, the amount of matter at the end of the change equals the amount of matter before the change. This is known as the Law of Conservation of Matter. Energy can change forms. When energy changes forms, the amount of energy before the change equals the amount of energy after the change. This is known as the Law of Conservation of Energy. The system of bookkeeping for energy is thermodynamics. Energy can be used to cause change in matter. For example, UV or gamma radiation can break bonds. Energy can change into matter and matter can change into energy. Such reactions are not ordinary, but rather nuclear chemistry. The sum across mass and energy at the beginning of the reaction must equal the sum across mass and energy at the end of the reaction. This is known as the Law of Conservation of Matter and Energy. Energy forms we studied include (but are not limited to): Kinetic energy energy of motion; related to temperature Potential energy stored energy; related to bond strength, also related to voltage and to height Electromagnetic energy light energy; related to frequency of light waves, heat energy (infrared) Sound energy noise Mechanical energy term used for machines; related to kinetic energy Electrical energy electricity Nature tends toward lower energy. Nature preferentially and spontaneously tends toward lower energy. Work is required to prevent such spontaneous reaction. Nature tends toward greater stability, expressed as stronger bonds. In order to achieve lower energy, substances must give away energy. Nature tends toward greater disorder (entropy increases).
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Walker CH304k Big Picture, Review, and Reference Materials Page 2 of 10 Structure is intimately related to function. Matter consists of substances such as atoms, molecules and compounds. Molecules and compounds have a structure associated with them. Molecular structure may be determined by a two-step process: sketching a Lewis Dot structure and determining the electronic and molecular geometry. A change in the geometry of a molecule changes the molecule’s function. For example, replacing chlorine atoms on a CFC molecule with hydrogen atoms results in a less-stable molecule that does not destroy the ozone layer. Molecular weight affects molecular properties. Heavier molecules sink more, float less. Heavier molecules require more energy to move them. Heavier molecules attract one another more than lighter molecules.
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This note was uploaded on 05/10/2008 for the course CH 304k taught by Professor Walker during the Spring '08 term at University of Texas at Austin.

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Main Ideas and Big Picture of CH304k_2 1up - Walker CH304k...

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