A&O 2 - Lecture 1.2

A&O 2 - Lecture 1.2 - • A condensed extremely large...

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1 Chemistry, Sun, Earth • More Definitions • Chemistry ! Reactions ! Lifetime • Sun and Earth ! Origins ! Blackbody Radiation Emission 2 Just a Few More Def’ns. • Compound—a molecule containing more than one element • Reaction—transformation of substances ! In a reaction, reactants ! products • Radicals—highly reactive substances, due to open molecular bonds or free electrons • Oxidation—addition of oxygen (substance is oxidized) • Reduction—removal of oxygen 3 • Organic compound—contains hydrogen and carbon • Hydrocarbon—contains only hydrogen and carbon 4 Chemical Reactions Spontaneous Photolytic/ photodissociation Collisional A ! B A + photon ! B A + B ! C + ···
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5 Chemical Lifetime Half-lifetime: time to reduce amount of reactant to half its original amount e-folding lifetime: time to reduce amount of reactant to 1/e of its original amount • With highly reactive reactants, ! Fast reaction time ! Short lifetimes for reactants ! Usually results in small amounts of reactants present 6 The Sun
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Unformatted text preview: • A condensed, extremely large mass of hydrogen (90%) and helium (9.9%) • Fusion of hydrogen into helium produces energy to drive sunlight-producing reactions ! Most of the radiation eventually emitted to space is visible light 7 Electromagnetic Radiation (EMR) ! Wavelength 8 Ultraviolet Visible Infrared Short wavelength Long wavelength 9 Blackbody Radiation Emission • Blackbody: an object that absorbs all wavelengths of EMR that fall on it ! Also emits radiation at all wavelengths ! Emission spectrum is temperature-dependent 10 Intensity ! max Wien’s Law: the wavelength at which a blackbody emits the most radiation is inversely proportional to the blackbody’s temperature max ( μ m) = 2897 T (K) 11 Solar/terrestrial Radiation 12 Sun and Earth are both near-blackbodies I Sunlight Terrestrial radiation Sun, 6000K: emits mostly visible light Earth, 255K: emits mostly infrared radiation...
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This note was uploaded on 10/04/2009 for the course A&O A&O 2 taught by Professor Lew during the Spring '09 term at UCLA.

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A&O 2 - Lecture 1.2 - • A condensed extremely large...

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