Being Chemists this week!

Chemical Identification—Identifying the Unknown

This Tuesday, we examined six white powdery substances and performed experiments to help us identify what each one could be. The six substances were all very common household items- baking soda, cornstarch, sugar, salt, chalk, and borax. We examined which of these substances were soluble in water and in alcohol, which ones reacted with vinegar and which ones turned a color in the presence of iodine. We found that each white powder has its own set of characteristic physical properties and chemical interactions with our test solutions. For example, baking soda reacted vigorously with vinegar (ever tried a homemade volcano? It’s usually baking soda and vinegar that create the bubbling “eruption”), while cornstarch turned a cool blue color when we added iodine to it. We learned that “you can’t judge a book by it’s cover” any more than you can judge what a white powder is by just looking at it. In both cases, experimentation or further analysis is needed to find the true identity of an unknown!

Identificación de sustancias químicas

 En la clase de hoy examinamos seis sustancias en polvo de color blanco y realizamos experimentos para lograr identificarlas. Resultó que las seis muestras eran sustancias comúnmente utilizadas en nuestros hogares: bicarbonato de sodio, maicena (almidón de maíz), azúcar, sal, tiza y bórax. Examinamos cuales de las sustancias eran solubles en agua y/o en alcohol, cuales reaccionaban con vinagre y cuales cambiaban de color en presencia de yodo. Encontramos que cada una de las sustancias en polvo tiene su propio set de propiedades físico-químicos característicos. Por ejemplo, el bicarbonato de sodio reaccionó de manera vigorosa con el vinagre (¿alguna vez has probado hacer un volcán hecho en casa? Usualmente es una mezcla de vinagre y bicarbonato lo que crea la erupción), mientras que la maicena se tornó de color azul cuando le agregamos unas gotas de yodo. Podríamos concluir que “no podemos juzgar un libro por su portada” ni tampoco juzgar un polvo blanco solamente observándolo. En ambos casos, se requiere de análisis y experimentación para descubrir su verdadera identidad.

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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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