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
Exam time is coming and we have 1,100 freshman chemists getting stressed and nervous, so this is for them.
You need “stress” in your live. No stress would mean you would stay in bed all day. Well I’m a chemistry prof and like physical chemistry, and not a psychologist, but over the years you get to know students worries.
There are two types of stress. There is bad stress (“I’m scared”, “I’m dumb” “It is too hard?”) and there is good stress (“Great day, gotta get up!”, “I really want to understand stuff” “I am looking forward to tonight, so got to look good.”)
Use the good stress.Read More
In that pile of glass plates I found in the Kamerlingh Onnes laboratory in 1974, was the original glass negative of the 1927 Solvay Conference. I had never seen the picture before and it was an exciting moment as I looked at my find, and started to recognize individuals.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