A few months ago I was searching the internet, looking for a better way to teach stoichiometry to my pre-AP chemistry students. While my methods of dimensional analysis “got the job done” for most students, I would still always lose students and many lacked true understanding of what was happening in the reaction. I wanted to try something new that would promote a better chemical understanding. In my search for this elusive stoichiometry method, I came across Dena Leggett’s ChemEd X blog post entitled “Doc Save Everyone”, as well as other posts about BCA tables from Lauren Stewart, Lowell Thomson, and Larry Dukerich.
HCl and NaOH, a strong acid - strong base titration? Citric acid and NaOH, a weak, triprotic acid - strong base titration? Do your students standardize the NaOH solution as a first step?
The October 2016 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include: exploring the candy–cola soda geyser; peer-led team teaching; investigating students’ reasoning; fostering a student-centered learning environment; chemical education in India; activities to increase interest in chemistry; using a smartphone in the laboratory; food chemistry analysis; organic synthesis; green chemistry in the organic laboratory; materials science experiments; cost-effective laboratory equipment; teaching resources; JCE resources to celebrate National Chemistry Week 2016.
Common drain cleaners consist of water, sodium hypochlorite (bleach) and sodium hydroxide (base) and/or potassium hydroxide (base). Bases are caustic (caustic loosely means to gnaw or eat away at) and can cause corrosion in metal pipes. Wouldn’t you know, our house has PVC piping through the fixtures that dump into a 45 year old cast iron pipe. The cast iron pipe is old and currently shows signs of surface rust and corrosion to the point where the pipe appears to be leaking then sealing itself in several spots. Not to mention the interior of the cast iron pipe may not be completely open, thus, not permitting a fast flow in drainage. Good news: a home warranty is being taken advantage of to hopefully replace the cast iron pipe with a PVC pipe.
How does the blue to white color change occur in the foam of Scrubbing Bubbles or KABOOM Brand cleaners? Watch this video and find out.
I have a first day routine that I am very proud of. I have used it for 25 years and I think I finally have it down pat. I have spoken to students from 20 years ago at reunions and they tell me that they still remember the first day of chemistry so I think it is pretty good.
Last night I had the opportunity to do another lab that I wrote with my students. It is so exciting to see something go from words on a screen to a group of students working together in a laboratory. I learned so much as I walked around the room last night. Here are a few highlights:
The February 2015 issue of the Journal of Chemical Education is now available to subscribers at http://pubs.acs.org/toc/jceda8/92/2. The February issue includes content on: metal-organic materials, assessment, acid–base chemistry, game-based approach to teaching, chemical structure and properties, luminescence, inquiry-based teaching, nanochemistry, synthesis, and computational chemistry. This latest issue of JCE plus the content of all past issues, volumes 1 through 92, are available at http://pubs.acs.org/jchemeduc.
Students combine sodium carbonate and hydrochloric acid generating carbon dioxide gas which is allowed to escape. They measure the actual yield of carbon dioxide produced (missing mass), calculate the theoretical yield using stoichiometry, and then the percent yield. Students understand that 100% yield is the most appropriate answer (based on the Law of Conservation of Mass), so after considering the meaning of significant figures and the uncertainty of their measurements they are asked to decide if they did (or did not) get an answer that might indicate the validity of the Law.
One 50-minute period to perform the lab. One additional period to perform the calculations (optional). Often more able students will have time to begin some calculations at the end of the lab experiment.
Congratulations to Grazyna Zreda who solved the Chemical Mystery of the Mentos candies! To conduct this trick, two white Mentos candies are placed in separate beakers that both contain universal indicator.