Don’t judge a book by its cover!

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 (to them) white powders to test (baking soda, borax, salt, and cornstarch).  They then pooled their information in order to figure out who had which different substances.

They performed tests of three different properties: solubility, reactivity, and decomposition with heat, in order to identify their sample. They observed which powders dissolved in water and/or in rubbing alcohol, which ones reacted with vinegar (if a substance reacted with vinegar the students observed bubbling) or iodine (one sample turned purple!). Some classes also observed what happened when we held a sample over a flame (popping sounds, or the smell of toasted marshmallows!).  Some students also noticed that drops of iodine that accidentally got onto their papers also turned purplish-black, and this prompted lots of good questions and discussion.  Students did a great job staying focused on their experiments and using teamwork to collect all the data they needed.

Snapshots of the day:

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Author

Dr. Catherine Sukow

Dr. Sukow's interest in science education began when she was a teenager, with an extended visit to San Francisco's Exploratorium. In college, she had summer jobs in a similar, smaller, museum. She focused her Master's research at NCSU on the structure of metal silicides on silicon, and her Ph. D. work at Brandeis on the structure of crossbridged actin bundles. While volunteering in her childrens' schools, she was reminded how much fun it is to teach science, and is happy to be teaching now with Science from Scientists. In her spare time, she also enjoys yoga, choral and solo singing, and attempting a variety of international cuisines.

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