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Chemical reactions and thermodynamics

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  • 1. CHEMICAL REACTIONS AND THE LAW OF THERMODYNAMICS
  • 2. A review of energy
    • energy comes in many forms
      • thermal
      • nuclear
      • mechanical (including kinetic and potential)
      • electromagnetic
      • chemical
    • Living organisms use chemical energy to perform life functions such as active transport and mitosis
      • energy changes form but is never completely lost
  • 3. Two types of chemical reactions
    • Exergonic
      • a chemical reaction that releases energy by breaking bonds between molecules
      • occur spontaneously most of the time (sometimes requires a small amount of energy to get started)
      • example: breaking down food molecules during digestion
      • often these types of reactions produce heat
  • 4. Two types of chemical reactions
    • Endergonic reactions
      • bonds between molecules are formed
      • requires a good amount of energy to happen
        • this energy is called activation energy
      • often absorbs heat when reaction occurs
      • do not occur spontaneously, but only when energy is available
      • many cellular reactions are endergonic, therefore cells must have a way to store the needed energy for use in chemical reactions.
      • source of info: http://library.thinkquest.org/27819/ch4_2.shtml
  • 5. Theories versus Laws
    • Theory
      • Explanation of a set of related observations or events based upon proven hypotheses.
        • More like a scientific law than a hypothesis .
      • Verified multiple times by detached groups of researchers.
      • One scientist cannot create a theory, he/she can only create a hypothesis.
        • Examples : The theory of evolution, the theory of relativity, and the quantum theory .
  • 6. Theories versus Laws
    • Law
    • A statement of fact meant to explain , in concise terms, an action or set of actions.
    • Generally accepted to be true and universal by all of the scientific community
    • Can sometimes be expressed in terms of a single mathematical equation.
    • They are accepted at face value based upon the fact that they have always been observed to be true.
      • Examples : The law of gravity, Newton’s laws of motion, the laws of thermodynamics .
  • 7. The laws of thermodynamics
    • Thermodynamics is the study of energy
    • First law (law of conservation of energy)
      • states that energy is always conserved
        • it is not created or destroyed
        • it simply changes from one form to another
      • Example: the potential energy stored in a stretched rubber band turns into kinetic energy (energy of motion) when the rubber band snaps
        • total amount of energy stays the same
      • In short, the quantity of energy always stays the same
  • 8. The laws of thermodynamics
    • Second law (law of entropy)
      • states that even though the total amount of energy does not change in a system, the form of energy will increasingly go from usable (like chemical energy) to unusable forms (like heat).
      • this is called increasing entropy
        • entropy is the amount of disorder (chaos) in a system and as long as there is continuous energy transfer, entropy remains low.
        • laws of thermodynamics
        • second law of thermodynamics
  • 9. 2 nd law in relation to biology
    • Energy in living organisms is used for growth, repair, motion etc.
    • If this energy is constantly used for these things, without any input of more energy, the organism will die.
        • laws of thermodynamics
        • second law of thermodynamics
  • 10. Third law of thermodynamics
    • states that if all the molecules in the universe stopped moving (a natural thing that molecules do), a state called absolute zero would occur
    • this would happen when all matter and energy is randomly distributed in the universe (highest entropy)
    • would equal -273.15 deg. Celsius