From: Hauser, Michael (MHauser@stlcc.edu) Date: Thu Feb 13 2003 - 14:44:29 EST Next message: Nina Vehslage: "[Channel-talkchemistry] Fw: Acid Base light demo" Previous message: Nina Vehslage: "[Channel-talkchemistry] Acid Base light demo" Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] I thought the M&M half-life lab was simple but effective. For an advanced, kinetics based course, I would consider the following additions. Have the students graph the natural log of the M&M counts versus time. Since this is first-order data, the new graph should show y=mx + b behavior (a straight line). The slope of this line (the "m"), is the rate constant, "k". If the students use the relationship that half-life for a first-order relationship is equal to 0.693/ k, they can calculate the "half-life" of the M&Ms. They will have to assume an arbitrary unit of time like seconds, minutes, days, years, etc, but the point will be made. Don't forget to mention that the natural log of "one-half" IS 0.693, hence its appearance in the formula. If they plot their Ln data, their slope should be very close to the 0.693 value! Concerning the nuclear radiation lab, this is a neat way to alleviate a lot of the fears held by the general population of citizens. How appropriate in this day of "dirty bomb" terrorism threats and irradiated meat in grocery stores that we explore this topic. I do have a device from Black Cat Systems that hooks to a laptop and can measure radiation counts. My concerns: The course literature mentions that only a licensed lab and lab supervisor should have these materials. Is this true? Does it vary by state? Also, when you purchase the radiation sources, how long do they last? Do you need to constantly buy new sources? Michael Hauser Next message: Nina Vehslage: "[Channel-talkchemistry] Fw: Acid Base light demo" Previous message: Nina Vehslage: "[Channel-talkchemistry] Acid Base light demo" Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]