The Beginning of the End

I learned a few things about pressure last week. It started when I looked at my syllabus and realized that there are only two chapters between me and the final exam. Suddenly, visions of my first day as a bumbling novice loomed large with lots of sweaty details. Then my usually latent test anxiety kicked in. I agree with philosopher Peter Koestenbaum that anxiety “is not something to get over” and that understanding it is “the beginning of an authentic life”, but between the writer’s block and the sleeplessness I was not having fun.

Fortunately, we chemists know how to use pressure to our advantage. We compress gases every day so that you can fill up tires and basketballs, transport truckloads of hydrogen, and dispense just enough helium to make funny voices.  The Ideal Gas Law, PV=nRT, gives us a way to understand how pressure (P) varies with the volume of the container (V), the amount of gas molecules (n), and temperature (T). R is a constant that holds it all together. Solving for P= (nRT) / V we see that as volume goes up, pressure goes down. As the amount of gas or the temperature increases, the pressure also increases. This is probably the most intuitively obvious formula that exists.

Since there is no formula for self-inflicted pressure, I decided to change my isolating equation of study+quiz+blog+repeat by adding a reality constant. First step: I scheduled my final exam for February 27th. It felt good to take control of my fate, or at least my schedule. My home coach always encourages me to get classroom time during my training, so I contacted Appleton City Public Schools and Rockhurst High School for some classroom observation and substitute teaching. Finally, I talked to a retired teacher. Her repeated assurances that there is no amount of work that will adequately prepare me for the first year were not reassuring. However, I did appreciate her recommendation to attend Interface 2014, which is a three day conference sponsored by Missouri University and the Missouri Department of Education for high school Math and Science teachers.

Will I find other people that feel the same way I do about Chemistry? Will I find my “Community of Truth”, so beautifully drawn by Parker Palmer, in The Courage to Teach?  Stay tuned.

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Are You a Tortoise or a Hare?

Are you quick to react? Once you start, is it over and done or do you go on and on? Those of you with even minimal social skills (a fair question given your choice of reading) know that our reactions depend on two factors: energy and the situation.

Molecules need Activation Energy to start a reaction and if their bonds are weak they need very little. However, if the bonds are strong and the Activation Energy is too high, increasing the temperature or adding a catalyst will get things going. Catalysts provide an alternate chemical route that requires less energy, like those facilitators that get everyone else in the room talking, without becoming consumed in the reaction.

Once a chemical reaction starts, molecules mill around for a while in what is called the Transition State and they may even form some intermediate compounds. Molecules need to bump into each other to react, so increasing the temperature, concentration, and surface area all increase the likelihood of of contact and reaction. This is described by the Theory of Kinetics and Open Office Design. Fortunately, unlike workplace interactions, chemical reaction rates can be described mathematically.

Six factors affect the overall reaction rate: temperature, concentration, collision angle of molecules, frequency of collision, and the nature of the reactants. This set of variables makes for a complicated situation which was elegantly described by Svante Arrhenius in 1889.

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K is the rate constant, A is the prefactor which describes the orientation of the molecular collisions, T is the absolute temperature at which the reaction is taking place, Ea is the activation energy, and R is the Universal gas constant. One simple expression accounts for every factor that governs every reaction.

Do your loved ones or workmates complain about your pace? Explain that it’s simply the product of your variables and invite them to experiment. Who knows what discoveries await.

Next Week: The Beginning of the End

Life, Death, and Chemistry

Look around – can you imagine how many chemical reactions are happening before your eyes at this very moment? Some materials are synthesizing and some are decomposing. Some compounds are swapping molecules and some may combust. Without these reactions and our ability to predict them, there would be a smaller staff at Downton Abbey, tonic would stay fizzy, nausea would last, and the New Year would be quiet.

The most important example of synthesis occurs when hydrogen and oxygen molecules combine to make water. This is as simple and profound as creation itself. A less inspirational example of synthesis is the formation of tarnish that occurs when silver reacts with sulfur in the air to make silver sulfide. Chemists call this 2Ag + S —> Ag2S and Lord Grantham calls it a steady job.

A sad example of decomposition is the spontaneous decay of carbonic acid (H2CO3) into carbon dioxide (CO2) and water. This is why that large bottle of tonic that you have been saving for the summer G&T’s may ultimately disappoint: H2CO3 ——> CO2 + H2O.

The most interesting reactions happen when compounds swap, or replace, molecules to form new substances. Hydrochloric acid (HCl) in the stomach makes us queasy until calcium hydroxide (Ca(OH)2) arrives. Oh what a relief it is when the acid is neutralized into two products that are much easier on the stomach: calcium chloride (CaCl2) and water,  2(HCl) + Ca(OH)2 ———> CaCl2 + 2(H2O).

For sheer drama, however, no reaction can match combustion. Fireworks are made with gunpowder that produces  heat and noise and metals that produce color. Copper shows blue, lithium and strontium red, and magnesium and aluminum are white when combusted. Combustion reactions produce much more energy than is required to start them and they need a lot of oxygen. Drama turns to danger when materials spontaneously combust, which happens when enough heat is generated by the reaction to ignite the materials at hand. This can happen with the right combination of microbes, moisture, heat and hay.

The laboratory of my life got a lot more reactive this week as I am making plans to use my favorite Christmas gift:  a Chemistry Set with enough equipment and reagents to conduct 333 experiments. My husband (aka Santa) has offered to help me set up an area in the garage and has even volunteered to be my assistant on the condition that I call him ‘Igor’. It’s all about the chemistry.