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.Read More
n 1887 J.J. Thomson discovery of the electron was a significant step that led to a much deeper understanding of the microscopic properties of Nature. In this entry, I will discuss the famous Millikan Oil drop experiment which was done in 1909.
But recall that in his characterization of the properties of the electron he could only determine the charge to mass ratio, given by -1.76 times ten to the 11th Coulombs per kilogram. Was this ratio a result of two big values or two small values?
Robert Millikan was able to separate the ratio in order to show that the ratio was that of two small numbers and in this way he was able to extract the elementary charge and the electron mass. Comparing the electron mass to that of the lightest element, Hydrogen, it is found that the mass of an electron is 1800 times smaller. Indeed at that time this was the smallest particle known.Read More
Discussion of the discovery of the electron by J. J. Thomson in 1897 using a cathode ray tube. He was able to obtain the charge to mass ratio, but not the actual mass or charge. Later Millikan was able to separate the two. Indeed Thomson found a new state of matter which laid the foundations for quantum mechanics and a huge range of technologiesRead More
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...Read More
Summary of MCH High School and College Chemistry and Physics Each of our five courses covers all the material and more that are found in chemistry and physics courses from the high school to College level. The courses entail between 100 and 200 hours of study each. They have between 6 and 8 hours of short, concise spoken comments to explain the ideas and to guide you. (In comparison, if you take a course at college, you usually have about 32 hours in class). Our voice comments are focused as clear. There are hundreds of interactions throughout all the programs that engage you and give you effective ways of understanding the concepts of science. One of the major advantages is that you can do them at your own pace in front of your computer whenever you want. Let’s briefly look at the TOC of the products: you can find more information by clicking on the appropriate product link. High School These assume that you have no background at...Read More