Sunday, January 27, 2013

The End of the Dreaded Lab Report

I am pretty sure that starting next year I will no longer require the students write a formal lab report (i.e., title page, purpose, procedure, data, conclusions) which is due the following week.  Instead students will have to complete a set of directed questions pertaining to the purpose in class and a set of questions outside of class.  The questions outside of class will be done online for the most part.  Half of the credit will be for completion and the other half is for their understanding of the results.  This will be for all chemistry classes which includes College Prep, Honors, and AP Chem.  Seymour High School is getting rid of the Core class designation next year and those students will be incorporated into College Prep classes.

Why get rid of the formal lab reports?  There numerous reasons but one that sticks out is my beloved technology.  Years ago students had to research lab questions, construct tables and graphs based on the experiment, and put them into a handwritten report.  Now, they look up the info online and just cut and paste it into the report without reading it or comprehending it.  I prefer they construct tables and graphs with the computer, however, I am not sure who did the graph these days.  In addition, they will send this to their friends who change a couple things or not and submit this as their own work (notice I didn’t use the word plagiarize - that’s another blog post).  I could require students to hand everything in by hand but I think this new approach will be friendlier for less motivated students.  Also, this takes care of another issue, absenteeism.  If a student misses the experiment, I can give them some data so they can complete the questions.  Of course it would be easier if they were there for the experiment.

Lab reports are important but the implementation or grading is not antiquated well with the times.  I haven’t the time to set up the lab, take down the lab, grade the report, and then ensure that each student completes their own report.  Universities and Colleges typically have Lab as a separate course where a Teaching Assistant does the work.  

I have discussed this with Tony Ciccone, Seymour Chem Teacher emirates, as well as a colleague in another district who no longer requires formal lab reports.  He has very good results especially with his AP Chem class.   I think this new approach will be less time consuming for me once it is implemented and more importantly, better for the students.

Comments are welcome, especially from other HS chem teachers...

Wednesday, January 16, 2013

How Safe Are Post 1982 Pennies To Eat?

I remember being very young and having my mother yell at me when I got near change. Why?  My sister swallowed a penny when she was a toddler.  Of course my contacted the doctor who said keep a watchful eye in the toilet for the next 24 hrs.  As it so happens, my mother was able to retrieve the coin without too much fanfare but did not want to go through the experience with me.  This was in the late 1960's - early 1970's and stomach acid does not react with copper.

Prior to 1982 pennies were made of pure copper.  However, the price of copper rose to such price that the copper was worth more than the penny.  To avoid massive amounts of people getting rich by turning in their copper Lincoln's for cash at the scrapyard, the U.S. Mint made pennies out of a cheaper metal, zinc, and just plated them with copper.

Why the nostalgia, my students recently did a fun activity where they calculate the percent composition of a post 1982 penny (97.5% Zn, 2.5% Cu) by putting four small niches on the sides of a penny and soak it in 6.0 molar hydrochloric acid (HCl) for 24 hrs.  The next day what is left is a shell of a penny as HCl dissolves zinc (Zn) but does not touch copper (Cu).  Stomach acid is also made of HCl (pH around 2), thus if you swallowed a new penny with a notch in it, the stomach acid would dissolve the zinc and release hydrogen gas in the process.  Avoid sparks when you burp!

Although stomach acid with a pH of 2 corresponds to a 0.01 molar solution of HCl and we used 6.0 molar HCl, it is still strong enough to dissolve some of the zinc.  You probably don't have to worry about flaming burps but it could cause ulcers (source: Chicago Tribune).

Zn + 2HCl  -->  ZnCl2 + H2

Thursday, January 10, 2013

The Blog of Phyz: Forty years before The Mechanical Universe

Great Videos from Dean Baird!

The Blog of Phyz: Forty years before The Mechanical Universe: The Mechanical Universe is no spring chicken. It was born in the mid-1980s. I recently stumbled across this old gem on YouTube. As a fan ...

Tuesday, January 1, 2013

Uncle Amedeo!

Amedeo Avogadro was (1776-1856) was an Italian scientist who was born in Turin.  He came from a well-to-do family of lawyers and became a lawyer himself.  However, he was more interested in natural sciences and in 1800 began studying physics and math.  In 1809 began teaching science in high school in Vercelli.  In 1811, during his teaching teaching tenure he published an article which contains probably his most famous contribution to science aptly named Avogadro's law (a.k.a. Avogadro’s hypothesis).  In a nutshell, he proposed that the volume of a gas (at a given pressure and temperature) is proportional to the number of atoms or molecules regardless of the nature of the gas.

The number of particles in one mole of substance, 6.02 x 1023 , is known as Avogadro’s number in his honor and was never actually calculated by Avogadro due in part to the technology of the time but his understanding made it possible for later scientists to calculate it.  A rudimentary estimate was first proposed by Johann Josef Loschmidt in 1865 but was not measured accurately until 1909 by French physicist Jean Perrin

Avogadro's private life seems to be a mystery or at least scandal free.  He married Felicita MazzĂ© and had six children.  It has been suggested that he sponsored some Sardinian revolutionaries, who were eventually stopped by the announcement of Charles Albert's constitution in 1848.  Also, I have been unable to disprove the claim from my chemistry colleague, Antonio Ciccone (also from Italy), who keeps telling his students that Avogadro was his uncle.

wikipedia: Amedeo Avogadro