The lab activity shared here is a simple experiment where students use stoichiometric principles to experimentally determine the amount of sodium bicarbonate in an Alka-Seltzer tablet. Novice students tend to find stoichiometric calculations difficult, so practicing the calculations on a pre-lab assignment boosts their confidence and ultimately leads to more successful labs. The Asynchronous Video Pre-Lab Assignment shared here demonstrates the procedure and the calculations required in the experiment.
Students use a micro-scale method to extract caffeine from tea using dichloromethane. At the end of the activity, the students' dochloromethane extractions are pooled; the solvent is distilled after class for re-use.
In this lab, students connect the workings of an electrochemical cell in the lab with the symbolic equations used in electrochemistry and manipulate a model representing the particulate level of what is happening during the electrochemical process. Although this lab was previously highlighted on ChemEd X, there are now virtual options offered!
Infrared technology (FLIR Cameras) can be used to investigate intermolecular forces.
Heidi Parks offers a soap-making lab or activity that can be run in a chemistry class with 25-30 students working at the same time. She usually does this activity right before spring break, as it provides enough time for the soap to harden and cure (high school students are impatient to use their soaps right away, which you should not do with cold process soap). She has used this soap making activity at different points in the curriculum: during intermolecular forces during acids and bases, and during stoichiometry.
I found a version of this demonstration online a couple of years ago. I admit, when I first tried it with my class it was mostly for a crowd pleaser to demonstrate the activity series of metals, but I then became very intrigued by the processes occurring. The original source only referenced the “single replacement reaction” between Mg(s) and AgNO3(aq). Therefore, when I saw a grayish product (silver) I was not surprised. However, I was surprised by the white flash and the production of a white product, which were reminiscent of the classic combustion of magnesium demonstration. This led to some research and my conclusions that follow. Read through to the end and you will find a video of the demo.
I have used several different versions of the Silver Mirror or Tollen's Test lab. I am sharing the method that has proven to be the most reliable for me. The solutions should be made fresh, the directions must be followed closely and timing is very important. I like the fact that relatively small amounts of the chemicals are required, but as always you must be vigilant with safety precautions.
Just this week I'm reviewing equilibrium with my IB Chemistry seniors after they finished some summer study on the topic. One of our classes was spent manipulating a classic equilibrium involving copper ions and a copper-chloride complex ion.
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.
Suitable for Online Instruction: An independent study on the chemistry topic of coordination compounds and complex ions suitable for AP Chemistry and first-year college chemistry students is presented. Originally published 3/20/2014.