Fizzy Drink Stoichiometry

Last year I stumbled across a lab for stoichiometry that has students create carbonated Kool-Aid by combining food grade citric acid and baking soda in their drink.  It worked beautifully, and we completed it again today.  I bought four packets of generic fruit punch drink mix, a bag of sugar, one box of baking soda, plastic spoons, cupcake paper wrappers for measuring the powders on the balance, enough red plastic cups for each team to have one, and enough small Dixie cups for each student to have one.  The food grade citric acid was a bit harder to find.  I called around to grocery stores after reading that it was used in canning, but no local shop had it in stock.  They sweetly offered to order it for me, but I figured I could do that myself.  I ended up purchasing a small jar online.  Each team of four students uses less than one gram, so the 100+ gram small jar is more than enough, and not expensive at all. Citric Acid


Students first taste the drink alone, drink + citric acid, then drink + baking soda.  It's a very dramatic response when they taste them.  I always stress that no one is required to eat/drink anything they don't wish to, but I encourage them to try it if they feel comfortable doing so. 

The final part of the experiment is to

1) write a balanced equation for the reaction between citric acid and baking soda
2) calculate the quantity of baking soda that would react completely with 0.30 g citric acid.
3) mix your calculated quantities together in the drink.  If calculations are correct it's lovely and bubbly, but not sour or salty.
4) answer analysis questions about the work, including several more three step stoic problems leading toward the idea of limiting reactants.

 I'm very happy with the science involved, the dramatic student interest, and the content ties to real life in such a simple way.  I think this lab will be a winner for years to come.


The activity HERE is very similar to what I use, although I've modified the questions to suit my curriculum.

Lift a Flap Stoichiometry Practice

When we move from one step conversions to three-step stoichiometry problems, students struggle at first.  The idea that they must combine three different conversions confuses them, and they need some support.  Often, they need individual help more than I can offer, with lots of them needing my help and only one of me available.  One solution I've found to this problem is "Lift A Flap" Stoichiometry Practice.



Students are given a regular stoich worksheet with three step problems (just like our practice the previous day, with new numbers and reaction examples).  Set up around the room are eight stations with the problems worked out for them, but hidden under little paper flaps.  They can peek to see how to set up any part of the problem they want, or they can just check their answers.





This activity isn't for a grade, as that just encourages them to copy the answers without thinking about the process.  They know that tomorrow we're going to be doing a stoich lab, and if they don't understand the process, they won't be successful in their lab.  This is a problem for two reasons - they will lose points tomorrow on the lab AND the lab is edible.  If they don't calculate the quantities correctly, their drink will turn out disgusting.  Hopefully tomorrow I'll take some photos and blog a bit about our Fizzy Drink Stoichiometry Lab.  It was a big hit last year, and I'm really looking forward to trying it again.

Diagnosis Success: Making Anatomy and Physiology Come Alive

Last spring I purchased a few new books from NSTA, one of which is titled "Diagnosis Success: Making Anatomy and Physiology Come Alive" by NH Maller.  I've implemented most of the book now, so i feel good about speaking to its success in my classroom.

The students pretend to be doctors, including starting with "Medical School" where they research four medical conditions (later seen in their patients), and reading and signing the Hippocratic Oath.

The book has four anonymous celebrity patients, and encourages you to choose popular faces from the entertainment industry to connect students to their work.  Each patient has a chart and over the course of six lab tests, students identify which condition the patient has and creates a final diagnosis.

Teachers are encouraged to support each lab test with information about a different body system, and covers the Urinary, Digestive, Blood, Lymphatic, Respiratory, and Endocrine Systems through the labs.  This has taken more time than I anticipated, but the students have stayed engaged each time I bring back their "Celebrity" patients and updating their medical charts.  I've kept manila folders in the class for each group to keep their lab results and patient charts in, so they're always accessible.

Some of the labs are a bit gross (digestive by-products), or socially edgy (HIV test), but the students have really enjoyed the work and I think they see a more powerful connection to WHY we might want to know how the body systems work.

One of the best things is, when I had a question I was able to email the author from her website, and she responded to me the next day (question about materials needed for a lab).  She was very friendly and helpful, and was interested to hear how the implementation worked out in the classroom.

Overall, I think this term was very successful, and the increased student engagement was compliments of Maller and her new book.

Oxidation Reduction Batteries

Last year when teaching about Redox reactions in Chemistry, I could feel my students lack of energy and imagine little floating Z Z Z Z zzzzzz over their heads.  I decided this year to do something a bit more interesting, inspired by a blog called Kitchen Science by the Naked Scientists.  They referenced a YouTube video where the author shows charging his iPod with a fruit battery.

I downloaded one such video, and used it as a jumping off point with my students to inquire, "Can you charge an iPod with a fruit battery?"  We spent 6 days on this short PBL project, and it was completely student driven.  Students were shown the video (hoax), and shown a real example in a Two-Potato Clock that I bought at a garage sale last year for $1.  

After students journaled about how they think the clock works, they chose groups and researched their own food batteries.  They had one day in the computer lab to research and develop their own experimental plan, including safety information, materials lists, step by step instructions, and blank data tables.

We had two days in class to perform experiments, and access to several types of wire, metal plates, alligator clips, multimeters, and potatoes.  Anything else needed to be brought from home.  They also used a Kill a Watt meter to measure how much energy their own phone or iPod charger uses, so they can make a direct comparison between their battery and charging the device.

At the end of collecting their data, we spent one day on direct instruction of what redox reactions are, and how they power the two potato clock example from the first day.  They compared their understanding from their journal on day 1 to their understanding after this activity.

Lastly, students used this new information and photos they took during the experiment to develop a two slide presentation for the class.  They included diagrams / photos of their most successful batteries, and the chemical reaction that was causing the flow of electrons (including identifying what was being oxidized and what was being reduced).  This quick two slide presentation provided a nice quick conclusion of their work, as well as reflecting on what they could have done to make their battery better in the future.

At the end of the class on the final day, we compared the data collected by students (amps and volts), and determined there was no way the initial video was real, it was indeed a scam.  One of my students said we'd "busted" the myth.  I'm just glad we learned about Redox with less pain than last year, and hopefully making more of a memory for the future.