Chemical Identification—Identifying the Unknown
Students became chemistry sleuths in the science lab this week. In this lesson, we discussed how to identify a chemical without the use of complicated machines. Students learned that in addition to using their senses, they could also use chemical properties for identification. Each group of students was given two unknown white powders to test (the possibilities included baking soda, borax, salt, sugar, chalk, and cornstarch) and using the data they collected from a series of 4 tests, they were then pooled their test results to identify each powder.
They performed tests of a physical property (solubility), and two chemical properties (reactivity with acetic acid and with iodine) in order to identify their samples. They observed which samples dissolved in water and/or in rubbing alcohol, which reacted with vinegar or iodine (if a substance reacted with vinegar the students observed bubbling, and if a substance reacted with iodine, it turned purple!). For two samples, we also observed what happened when a sample was held over a flame (popping sounds, smoke, and the delicious smell of caramel!). Students did a great job staying focused on their experiments and collecting the data they needed to identify the unknown.
We’re looking forward to seeing you one more time before you get ready to finish your elementary school days!