The students have been learning and studying the properties of matter – physical and chemical. Physical properties describe characteristics of matter that you can observe or measure without changing its chemical identity, while chemical properties describe how a substance reacts to form new substances. Additionally, they learned about the six ways to test and determine properties of unknown matter, which include appearance, pH test, density, flammability, reactivity, and toxicity. To bring the unit of study from concepts to application, Dr. Danielsson tasked the students with using their knowledge of the scientific properties of matter to determine the identity of three different unknown liquids in a lab activity.

Prior to the start of the lab, the students were broken up into groups of two and provided with a plastic tray, a plastic pipette, a paper towel, and a sample of either liquid A, B, or C. At their tables, each pair worked together through the procedural steps of the six different tests. Dr. Danielsson reminded the students to write all their findings on the data sheet and cross-reference with their fellow class groups for the other liquid samples. For the first test of appearance, one student pipetted 15 drops of the liquid into one well of the tray and wrote the findings on the data table. For the second test of acidity, the other student dipped a strip of pH paper into the well and observed/matched the color change of the liquid to the pH scale. In the third test, the students pipetted 15 drops of the liquid into a new well and added one drop of potassium thiocyanate to determine toxicity as a positive result would turn red.

The next tests focused on density and reactivity with the students using a washer and alka-seltzer tablet as the materials placed in the liquid. For density, the students gently push down the washer in the plastic beaker to observe if it floated or not followed by adding the tablet in the beaker to observe the presence or absence of bubbles. The final test for flammability was conducted as a full class with Dr. Danielsson carefully placing a flame on the samples.

Following the lab activity, all the students worked independently on an analysis report using their observations, data table, and the provided list of possible options to determine the unknown liquids. The options were water, vinegar, isopropanol, and glycerol. For the report, students had written two to three pieces of evidence to support their choice along with answering the final question: are all of the liquids hazardous using the three-step process of claim, evidence, and reasoning.