ANSWER KEY INCLUDED Use this lab to get some hands-on practice with the physical component of physical and chemical properties. Materials required: digital or other scales, weigh boats, graduated cylinders, beakers, stirring rods, salt, and water This lab is an excellent way to get your students practicing basic lab techniques like weighing with scales (taking weigh boat measurements, hitting "tare" and then measuring the mass of their reagent) and measuring fluids in a graduated cylinder by using the meniscus. While practicing their technique, students will consider the physical properties of the simple saltwater solution that they are making. The lab asks them to evaluate whether they are observing physical or chemical properties and why, and also gets them to differentiate between homogeneous and heterogeneous mixtures. It challenges them to come up with a way that their solution could be physically separated, which provides evidence that their solution is in fact a mixture and not a compound. Students are also challenged to think of a scenario where they could change the weight of their salt without adding or subtracting any more salt. Their conclusion brings them to the realization that mass and weight don't measure the same thing. At the end of the lab, students will practice a basic density calculation using the numeric data that they recorded while measuring out the salt and water needed for this experiment.
