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Environmental Systems

Environmental Systems. Chapter 2. Chemistry quick review. Matter – mass + space Atoms – elements; periodic table; symbols Atomic number, mass number, isotope Radioactivity Radioactive decay, half-life Compounds – formulas Covalent bonds – molecules (very strong)

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Environmental Systems

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  1. Environmental Systems Chapter 2

  2. Chemistry quick review • Matter – mass + space • Atoms – elements; periodic table; symbols • Atomic number, mass number, isotope • Radioactivity • Radioactive decay, half-life • Compounds – formulas • Covalent bonds – molecules (very strong) • Ionic bonds – ions (slightly less strong) • Additional types of bonds • Hydrogen bonds – polarity (fairly weak)

  3. Water • Strong covalent bonds hold oxygen and hydrogen together • Oxygen is much more electronegative than hydrogen  it is an electron ‘hog’  the electrons spend more time around it than hydrogen  water is a polar molecule • The slight – charge on the oxygen side of the molecule is attracted to the slight + charge on the hydrogen side of another molecule (hydrogen bonding) • This polarity and hydrogen bonding of water causes all its other properties: • Surface tension • Capillary action • Specific heat • Density of ice • Solubility

  4. Important solutions • Acids • Excess H+ ions in solution • NNO3 (nitric acid) and H2SO4 (sulfuric acid) • pH < 7 • Bases • Excess OH- ions in solution • NaOH (sodium hydroxide) and Ca(OH)2 (calcium hydroxide) • pH > 7

  5. Matter • The law of conservation of matter • It’s a LAW! Chemical reactions must obey! • How does this impact the environment? • There is no ‘away’… • Compounds • Inorganic – no carbon or no carbon bound to hydrogen • Organic – have carbon-carbon and carbon-hydrogen bonds • Four important ones: • Carbohydrates • Proteins • Lipids • Nucleic acids (DNA & RNA)

  6. Energy • Energy - the ability to do work; power – the rate of work • Forms of energy: • Kinetic – energy of motion • Potential – stored energy • Temperature • Kinetic energy of the molecules within a substance • Energy has laws too! • First law of thermodynamics • Not created or destroyed, just changed • Second law of thermodynamics • Changes in energy result in a decrease in usable energy and an increase in entropy

  7. Systems analysis • Open system: exchanges of matter or energy • Example – a lake: water flows in as well as out • Closed system: no exchanges of matter or energy • Example – not as common; some underground cave systems • Which is Earth with respect to matter? How about energy? • Steady state systems • Input = output  system is not changing over time • Most natural systems are in a steady state due to feedback • Negative feedback loop – system returns to original state by decreasing its rate of change (resists) • Positive feedback loop – system accelerates by increasing its rate of change (amplifies)

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