Chemical reactions and thermodynamics

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Chemical reactions and thermodynamics

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

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