# Thermodynamics

4. Jul 2020
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### Thermodynamics

• 2. Introduction ..  All organisms require energy to stay alive  Orgamisms are energy transformer  Organisms take energy and transduce it to new forms  All chemicals reaction in cells involve energy transformations  For example green plants transform radient energy into chemical energy.
• 3. Forms of energy .. Energy Kinetic energy Energy in motion Light, heat, electric power Potential energy Stored energy Dam, battery wood, fossil fuels
• 4. Kinnetic energy.. It is the energy of motion observable as a movement of a partial, or set of particles.
• 5. Potential Energy.. Is the Energy by virtual of an objects position related to other object .
• 6. What is system ?  An assemblage of matter, which can interact with energy is called a system  A system is separated from its surroundings by a boundary. 1. An open system 2. A closed system 3. An isolated system
• 7. Open System..  An open system exchanges matter and energy with its environment  Biological system are open E.g. living cells, living things  Earth is an open system.
• 8. Closed system..  A closed system exchanges only energy with its environment. E.g. universe  When heat flows out of the system, the energy of the system decreases.  When heat flows in, the energy of the system increases  If the heat remains constant, it may be called an isotheral system.
• 9. Isolated system..  An isolated system exchanges neither matter or nor energy with its environment  An isolated system has boundary which is impermeable to both and all forms of energy.
• 10. The First Law of Thermodynaics..  Law of conservation of energy – Robert Mayer  “The first law states that the total energy of system plus its environment remains constant”  This law declares that “Energy is neither created nor destroyed in the universe and it allows to be exchanged between a system and its surroundings.”
• 11. Gibbs Free Energy..  The driving forces of a chemical as two components  ∆H is the drive toward stability (enthalpy)  ∆S is the drive toward disorder (entropy)  ∆ G is the net driving force of a chemical reaction.  V G values depend upon temperature, pressure and the concentration of the reactants and products.  If ∆ G<0 = the reaction is spontaneous  If ∆ G>0= the reaction is non-spontaneous.  If ∆ G=0= the reaction is at equilibrium Joseph Willard Gibbs
• 12. Second law of thermodynamics… Also called law of the degradation of energy or law of entropy This law was developed in 1850s by German Physicist Rudolf Clausius. This law states that “a system and its surroundings always proceed to a state of maximum disorder or maximum entropy”.
• 13. Concept of entropy (∆S)..  The word entropy (from Greek entrope=change) is a measure of the unavailable energy resulting from transformations  The term is used as a general index of the molecular disorder associated with energy degradation.  Second law implies that the entropy of the universe is increasing because energy conversions are not 100% efficient. i.e some heat is always released.  Second law also implies that if a particular system becomes more ordered, its surroundings become more disordered.
• 14. The Third law of thermodynamics ..  The entropy of a system approaches a constant value as the temperature approaches absolute zero.  At zero temperature the system must be in a state with the minimum thermal energy. This statement holds true if the perfect crystal has only one state with minimum energy energy.
• 15. Concept of enthalpy (∆h) ..  Enthalpy is defined as a change in heat content or heat or formation of a system.  The change in enthalpy is given by ∆H= ∆U+P ∆V Where ∆U= internal energy change P= pressure V=volume ∆U=the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. ∆U=Q-W Where Q= heat added to system W= work done by the system
• 16. Two types of biochemical reactions.. Exergonic reactions (catabolic)  ΔG is negative  ΔH is less than zero  Increase in stability  Spontaneous movement towards equilibrium  Coupled to ATP formation  catabolism Enderogenic reaction (anabolic)  ΔG is Positive  ΔH is greater than zero  Decrease in stability  Non spontaneous  Movement away from Equilibrium  Coupled to ATP utilization  Anabolism