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Posted by on Aug 30, 2013 in Physical Chemistry, General Science | 3 comments

Physical Chemistry – Overview of Thermodynamics

In one example I use bond energies to calculate the energy per mole of sucrose and TNT (the explosive trinitrotoluene). Most students expect that TNT has more energy, but it turns out the two have about the same. So why is TNT an explosive (actually a conflagration)? TNT burns rapidly and involves a huge volume change. It is the rate of reaction (chemical kinetics) and the rapid volume change that causes the explosive damage. Then I can move to the thermodynamics overview.

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Posted by on Aug 6, 2013 in Physical Chemistry, General Science | 0 comments

Physical Chemistry—hotness and coldness

When I start into heat capacity I contrast the temperature of a substance with the feeling of hot and cold. A thermometer will tell you the temperature of a substance, but that does not tell you how much heat is present. If you touch something, you can tell if it is hotter or colder than your hand, but what about two substances at the same temperature?

Suppose outside it is -10 C (14 F) and there you find a piece of steel and a piece of Styrofoam. Which is colder? If you touch the steel it feels colder than the Styrofoam, but they are both at the same temperature. If you placed the steel on the Styrofoam, no heat will flow between them (Third Law of thermodynamics). Since your hand is much hotter than the objects, heat must flow from your hand into them.

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Posted by on Feb 20, 2010 in General Science | 1 comment

The Aufbau Principle

In this clip the Aufbau Principle of the electronic structure of the elements is shown as an example of the content of MCH multimedia’s General Chemistry tutorials.  The Aufbau or building up principle makes use of the Hydrogen Orbitals and the Pauli Principle. Buy the General Chemistry Tutorial from MCH Multimedia:  General Chemistry can be used alone or in conjunction with any introductory chemistry text book. In this module, all the topics found in AP (Advanced Programs in High School), and college level General Chemistry courses are covered.  Learn in depth by working through the modules which are presented with clear verbal instructions and descriptions about chemical processes.  There are many places where you can plot results and do...

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Posted by on Feb 4, 2010 in General Science | 0 comments

Plotting Chemical Kinetics–steady state

In this video one of the many uses of plotting in the ebooks is given.  The example is first order consecutive reactions where the rate equations for the the concentration changes are plotted.  By varying the rate constants so that the first is ten times smaller than the second, the steady state approximation is explained. Buy the General Chemistry Tutorial from MCH Multimedia:  General Chemistry can be used alone or in conjunction with any introductory chemistry text book. In this module, all the topics found in AP (Advanced Programs in High School), and college level General Chemistry courses are covered.  Learn in depth by working through the modules which are presented with clear verbal instructions and descriptions about chemical processes.  There are many places where you can plot results and do...

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Posted by on Feb 4, 2010 in General Science | 0 comments

Chemical Calorimetry

In this video step-a by-step description is given of a bomb calorimeter that is used to measure the internal energy of a sample.  If you burn as sample completely and measure the heat that evolves, you can find the thermodynamic internal energy.  Recall that internal energy is a state function and does not depend upon how the sample is burned.  Therefore if you burn a sample in a bomb calorimeter, say some cookies, the energy you measure is the same as released when you eat the cookie. Buy the General Chemistry Tutorial from MCH Multimedia:  General Chemistry can be used alone or in conjunction with any introductory chemistry text book. In this module, all the topics found in AP (Advanced Programs in High School), and college level General Chemistry courses are covered.  Learn in depth by working through the modules which are presented with clear verbal instructions and descriptions about chemical processes.  There are many places where you can plot results and do...

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