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 six known white powders to test (baking soda, borax, salt, sugar, chalk, and cornstarch) and using the data they collected from a series of 4 tests, they identified each.
They performed tests of two different properties: solubility and reactivity, in order to identify their unknown sample. They observed which samples dissolved in water and/or in rubbing alcohol and 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!). Working collaboratively, they determined the properties of each known sample.

 

Identificación de sustancias químicas – Identificando lo desconocido

En el laboratorio de ciencias de esta semana, los estudiantes se convirtieron en “detectives químicos”. En la clase discutimos cómo identificar sustancias químicas sin la necesidad de usar complejos instrumentos de medición. Los alumnos aprendieron que las sustancias químicas se pueden identificar utilizando las características físico-químicas de éstas. Cada grupo de estudiantes tuvo que realizar pruebas a seis sustancias en polvo de color blanco (polvos de hornear, bórax, sal, azúcar, tiza, y maicena­). Luego, utilizando los resultados obtenidos en las cuatro pruebas realizadas, los estudiantes lograron identificar una quinta sustancia, de la cual no conocían su origen.

Los estudiantes realizaron pruebas de tres propiedades diferentes: solubilidad y reactividad.  Observaron si las muestras se disuelven en agua o alcohol, o si las muestras tenían algún tipo de reacción con vinagre o con yodo. Por ejemplo, si una sustancia reacciona con el vinagre se observa burbujeo, en cambio si la sustancia reacciona con el yodo, ésta se vuelve de color morado. Al trabajar en equipo, lograron determinar las propiedades de cada una de las sustancias conocidas, y luego con estos resultados lograron determinar la identidad de la sustancia desconocida, la cual resultó ser una combinación de dos de las sustancias conocidas. Los alumnos lograron mantenerse concentrados durante los experimentos y la recolección de datos e hicieron un gran trabajo al lograr identificar la sustancia desconocida.

Author

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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