Some Excel Toys
Part of what I want to do is have students use computer simulations as tools for experimenting with “what-if” scenarios related to the labs they do. There are many great simulations of general scientific phenomena out there, like the ones from the folks at PhET, but I need ones that correspond to the actual labs we conduct. So, I’m working on simulations that might fill this need.
Here are some prototypes that I’ve made for General Chemistry (you may need to download these to play with them - sometimes the macros don’t work via the web - in which case you’ll also need to allow macros to run when you open them):
Empirical Formula of a Hydrate
Granted, these may not make much sense without the context I would give students, but here’s a quick overview.
NaHCO3 Lab: Students use increasing amounts of acid to liberate the CO2 from alkaseltzer and then use reaction stoichiometry to find out how much NaHCO3 (sodium bicarbonate) was in the original tablet. The simulation lets you see what happens when you change the mass of the tablet or the concentration of the acid.
Hydrate Lab: Similar in spirit to the NaHCO3 lab in that students determine the composition of something by a measurement of mass loss. Here, they are finding the number of moles of water in a hydrate by heating a hydrated salt to dryness. They know the identity of the salt, so they can calculate the moles of salt and moles of water and then get the empirical formula of the hydrate. The simulation allows you choose different hydrates, see what happens when the heating efficiency is lowered, and to see what happens when you change the mass of the hydrate.
Thermochemistry Lab: Students mix various amounts of calcium chloride into water and observe the temperature change (a calorimetry experiment) to determine the heat of solution of calcium chloride. This requires them to interpolate a maximum temperature change from heating and cooling portions of the curve. The simulation allows you to adjust the heat of solution, the mass of the salt or water, the stirring efficiency (in the lab, this needs to be done well - they are trying to dissolve a solid), and the insulation efficiency of the calorimeter. They also are shown how the interpolation process works.