Energy and Forms of Energy

Energy and Forms of Energy - EnergyandFormsofEnergy...

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Energy and Forms of Energy Energy -work-heat Put Zn metal inside a container and pour in HCl (aq), H gas will be generated according to reaction. Zn (s) + 2HCl (aq)   ZnCl 2   (aq) + H 2  (g ) Case A: If we put a movable lid on the container, the lid will be  raised due to pressure generated by gas.  If the lid has mass m there will be the work done = W F∆l = W mgh Case B: If we put a non-movable lid on and place the container in  an ice bath, we will see ice melted. The ice bath temperature is raised. The   heat   is   transferred   from   the  container. Energy is the capacity to make change. o change in position                   work o change in temperature heat Note:  Energy from reaction comes from chemical bonds  System, Surrounding and Universe Universe  – everything, physical universe System  - part of universe which have special interest Surrounding  – the rest of universe There can be energy and matters transferring from and  to system. According to energy and matter exchange, systems can  be classified into opened   system   :   both   energy   and  matters   are   exchanged   (with  surrounding) closed system   :   only energy can be  exchanged isolated   system   :   neither   energy   nor  matter are exchanged Work motion against an opposing force 1. Mechanical work       W = -F l Opposing force has the same amount with force F but  opposite sign (-F) W = -mgh Opposing force = -mg (gravitation)
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2. Electrical Work W = fdq where: f   electric potential q    charge 3. Expansion Work W = -F l     = -(P ex A)  l W = -P ex  V Processes 1. Constant state a. Isothermal process  – constant temperature b. Adiabatic process  – constant heat c. Isopiestic process  – constant momentum 2. Reversibility a.   Reversible   process   -   can   move   back   to   original  position (slow and infinitesimal change) b. Irreversible process 
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This note was uploaded on 07/31/2011 for the course CHM 170 taught by Professor Lemtayo during the Spring '11 term at MIT.

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Energy and Forms of Energy - EnergyandFormsofEnergy...

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