Chemical Identification—Identifying the Unknown


Today, we examined six white, powdery substances and performed experiments to 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 changed color in the presence of iodine. We found that each white powder had its own set of characteristic physical and chemical properties that could be used for its identification. 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 what a white powder is by just looking at it. A careful observation/measurement of characteristic properties 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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Lauren Koppel

Lauren earned a Bachelor’s degree with a double major of Biology and Psychology from Clark University, and a Master of Education from the Harvard Graduate School of Education. During her undergraduate years, she worked in a evolutionary neurobiology lab that studied the neural development of annelids (marine worms), with a focus on the sox family of genes. Lauren loves learning about how the world works (including everything from biology to chemistry to engineering), and is passionate about sharing that knowledge and enthusiasm with others. In the past, she has interned at the Museum of Science, where she educated learners of all ages through hands-on activities, games, and experiments. Other science education organizations with which Lauren has worked include The People’s Science, EurekaFest, and Eureka! of Girls Inc. of Worcester. Currently she lives in Boston, where devotes her free time to playing Quidditch, reading sci-fi novels, playing her ukulele, and enjoying all the culinary delights the city has to offer.

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