Thermodynamics

Thermodynamics is an academic event with a building portion. Students are expected to build a box ahead of time that can retain the most amount of heat in a given volume of water. In addition, students must be able to predict the temperature of the water after a set time period and turn in a set of graphs showing the efficacy of the box. Lastly, a written test will be given about thermodynamic principles.

Event Details
The box and prediction are likely the biggest headache and the most important part of this event. The box must be no more than 20cm by 20cm by 20cm, have a 1.5 cm diameter hole on the top, and be constructed of wood, cotton, and other allowable materials.

When you make the box, insulation is the most important thing to consider. Examples of good materials for this are cotton balls and aluminum foil. Consider the types of heat transfer that may happen: conduction may be decreased by decreasing the amount of surface in contact, and radiation by having reflective materials. The structure of the box is also important, as being able to isolate the water from the environment may help you immensely.

Apart from the box, the prediction is extremely important in determining your score. From the event description, the prediction (being up to 25 points) can make or break this event. Thus, much testing must be done prior to competition. Make sure your testing environment is relatively stable and all factors such as humidity and room temperature noted down. Although the event description states that the volume can be extremely arbitrary, it is much more likely that the event coordinator pick a common volume, such as 100mL.

Lastly, make sure your graphs are neat, labeled, and have all 4 plots. Having 4 plots has a small and easy point advantage over less. In addition, accurate graphs and table will help you predict the final temperature exceedingly well.

The test can be composed of many sections, including but not limited to: multiple choice, matching, and open response. For the MA 2012 States test, the entirety was composed of multiple choice. Approximately half of the questions could be answered by conceptual knowledge of thermodynamics, while the other half required equations. Most of the equations necessary were common equations, such as $$q=mC \Delta T$$ and the Carnot cycle equations. However, there were some esoteric question, like one involving temperature at a certain depth in the earth given power output.

On the other hand, Nationals 2012 was composed of the three sections stated above. The matching section had simple terms such as: heat pump, convection, conduction, Carnot engine, and their respective definitions. The multiple choice had a combination of conceptual problems and definitions, such as understanding which law of thermodynamics this situation falls under, and mathematics, involving heat, engine equations, and expansion. The open response were mostly questions based off of $$q=mC \Delta T$$; however, there were also less obvious questions involving length changes due to temperature changes, a calculation of temperature based off of work done and efficiency, and a longer, ideal gas problem with p-V diagram. With a good resource, however, most of these questions are rendered trivial, and the building part a much greater weight in your placing.

Allowable Resources
One may bring a three-ring binder full of notes, hole-punched. This means, print out or handwrite as many resources as possible.

Incidentally, if we have acquired any past tests, use them. Seriously.

Helpful Hints
Start off with a page or two of just definitions. Even if they may be obvious, like the 4 Laws of Thermodynamics, it is useful to have them on there. Then, continue with equations, such as the Carnot cycle equations, basic heat equations, and equations for all of the different types of thermodynamic processes. Make sure to also have conversions on hand, even if they are obvious. Nobody wants to suddenly forget how many joules are in a large calorie; since you have unlimited notes technically, devote a page just in case. Lastly, although this did not appear on either the states or nationals level, the event description states that history may be tested. Thus, a page or two on specific peoples can be useful.

In addition, it is likely that the coordinators are lazy in terms of the temperature and volume of the given water. Thus, if time-crunched, it may make sense to test the obvious volumes and temperatures first. However, good planning means that more testing is never bad.