In “How strong an acid is vinegar?” the students explore the nonlinear relationship between the concentration of a weak acid and the pH of the solution. This formative assessment (FA) targets the question “how does structure influence reactivity?” Students need to understand the behavior of strong and weak acids to comprehend phenomena like buffering capacity.
In the How strong is vinegar? formative assessment students are guided by a worksheet and use a PhET simulation to visualize molecular level interactions. Students are first asked to predict the acidity of Glacial Acetic Acid. Then they are asked a series of questions to highlight their understanding of the structure of weak acids, including an exploratory simulation. Then, students are asked to predict the reactivity of Glacial Acetic Acid vs. Store Vinegar with baking soda. The initial questions in the FA are directed to gain understanding of student thinking and basic knowledge of key concepts. The students are then re-exposed to critical concepts through exploration. Finally, they are presented with a challenge to test their understanding. This FA was designed to be used with students in a 10th grade AP chemistry or honors chemistry classes.
I have not implemented this FA, however, in the future I am wondering if I need to extend the PhET simulation exploration questions to include dilution of weak and strong acids and related pH variation.
I have designed this FA for an asynchronous session. Where the FA Google Doc can be assigned through Google Classroom. I have linked videos (Youtube) explaining key concepts before students attempt the FA. In addition, videos related to skills, drawing on the Google doc, or writing chemical equations are also embedded in the FA.
If this FA was conducted in a face-to-face classroom session I would have set up demonstrations for the students and then asked them to make interpretations. However, since the document was designed for asynchronous learning it is designed in a way where students are asked to build upon their background knowledge and simulation exploration part of the FA. Students are then presented with a challenge where they have to predict instead of deducing a demonstration.
For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).
For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.
Other Safety resources
RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies