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- 1. Themodynamics
- 2. Energy <ul><li>the ability to do work </li></ul><ul><li>Kinetic – energy due to movement </li></ul><ul><li>Potential – stored energy </li></ul>Chemical potential energy is stored up in the bonds of a molecule.
- 3. First Law of Thermodynamics <ul><li>The total amount of energy in the universe is constant. </li></ul><ul><li>Energy cannot be created or destroyed. </li></ul>
- 4. H + H + H + H + H + - - - - -
- 5. Bond Energy <ul><li>Chemical energy is stored in the bonds of the molecules. </li></ul><ul><li>The energy stored in the reaction is called free energy because it is available to do work. </li></ul><ul><li>The symbol for free energy is the letter G (in honour of Josiah Willard Gibbs who developed the concept of free energy). </li></ul>
- 6. Bond Energies <ul><li>Measured in kJ / mol (kilojoules per mole) </li></ul><ul><li>Double bonds require more energy to break than single bonds </li></ul><ul><li>The greater the bond energy, the more stable the bond. </li></ul>Bond Type Average Bond Energy (kJ/mol) H-H 436 C-H 411 O-H 459 N-H 391 C-C 346 C-O 359 C=O 799 O=O 494
- 7. Bond Energies <ul><li>exothermic reactions – energy released </li></ul><ul><li>endothermic reactions – energy absorbed </li></ul><ul><li>energy is required to break bonds </li></ul><ul><li>energy is released to form bonds </li></ul>
- 8. Potential Energy Diagram EXOTHERMIC REACTION Why is that little hill labeled, Ac? Ac = activation energy. The energy required to release the free energy.
- 9. <ul><li>Activation energy is the amount of energy necessary to push the reactants over an energy barrier. </li></ul><ul><ul><li>The difference between free energy of the products and the free energy of the reactants is the delta G. </li></ul></ul>Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.12
- 10. Video Clips <ul><li>Hydrogen Explosion </li></ul><ul><li>http://www.youtube.com/watch?v=NYC23ANpEds </li></ul><ul><li>Activation Energy Example </li></ul><ul><li>http://www.youtube.com/watch?v=VbIaK6PLrRM&NR=1 </li></ul><ul><li>Activation Energy Song </li></ul><ul><li>http://www.youtube.com/watch?v=XgiCn1IpvzM </li></ul>
- 11. Exothermic Reaction
- 12. Potential Energy Diagram Absorbs energy
- 13. Second Law of Thermodynamics <ul><li>The universe is becoming more disordered. </li></ul><ul><li>entropy – a measure of randomness / disorder </li></ul><ul><ul><li>greater entropy = greater disorder </li></ul></ul><ul><li>metabolise glucose into CO 2 and H 2 O </li></ul><ul><li>C 6 H 12 O 6 + O 2 CO 2 + H 2 O + energy </li></ul>
- 14. <ul><li>Spontaneous processes are those that can occur without outside help. </li></ul><ul><ul><li>The processes can be harnessed to perform work. </li></ul></ul><ul><li>Nonspontaneous processes are those that can only occur if energy is added to a system. </li></ul>
- 15. Gibbs Free Energy <ul><li>Energy that can do work </li></ul><ul><ul><li>Heat is “useless” as it dissipates </li></ul></ul><ul><li> G = G final – G initial </li></ul><ul><li>For a system to be spontaneous, the system must either give up energy (decrease in H-enthalpy), give up order (increase in S-entropy), or both. </li></ul><ul><ul><li>Delta G must be negative. </li></ul></ul><ul><ul><li>The greater the decrease in free energy, the greater the maximum amount of work that a spontaneous process can perform. </li></ul></ul><ul><li> G is negative for spontaneous reactions (the rxn moves forward) </li></ul><ul><li> G is positive for reactions that require energy (rxn moves in the reverse direction) </li></ul>
- 16. Gibbs Free Energy <ul><li>Exergonic reaction – spontaneous, - G </li></ul><ul><li>Endergonic reaction – not spontaneous, + G </li></ul><ul><li>C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O G = -2870 kJ/mol </li></ul><ul><li>6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 G = +2870 kJ/mol </li></ul>Δ G = G final – G initial
- 17. G 20 240 140 20 140 240 Δ G = G final – G initial Please determine the activation energy and Δ G
- 18. Equilibrium Equilibrium reactions convert back and forth with minimal energy. For equilibrium reactions: G = 0
- 21. Adenosine Triphosphate <ul><li>ATP is the primary free energy source for cells </li></ul><ul><li>ATP ADP + P i </li></ul><ul><li>+ energy </li></ul><ul><li> H 2 O </li></ul><ul><li> G = -31 kJ/mol </li></ul><ul><li>in the cell, G is closer to -54 kJ/mol </li></ul>ATPase
- 22. Phosphorylation <ul><li>ATP hydrolysis does not occur on its own. </li></ul><ul><li>Often, the energy is focused through phosphorylation of enzymes. </li></ul><ul><li>ATP is replenished through cellular respiration. </li></ul>Reminder Hydrolysis – reaction reacts with water to break the molecule.
- 24. Redox Reactions <ul><li>reactions involving electron transfer </li></ul>
- 25. Redox Reactions <ul><li>Reduction – chemical reaction where an atom gains electrons </li></ul><ul><li>Oxidation – chemical reaction where an atom loses electrons </li></ul><ul><li>L oss G ain </li></ul><ul><li>E lectron E lectron </li></ul><ul><li>O xidation R eduction </li></ul>LEO the lion says GER
- 26. Redox Reactions <ul><li>Reducing Agent – substance that LOSES electrons; it causes the other substance to be reduced </li></ul><ul><li>Oxidizing Agent – substances that GAIN electrons; it causes the other substance to be oxidized </li></ul>
- 27. Redox in the Cell <ul><li>Many metabolic processes consist of chains of redox reactions. </li></ul>A - A B - B C - C D D -

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