Reactions and Results in Upper School Chemistry

A question many good teachers ask is, “How can I bring this lesson to life for my students?” In Parker’s Upper School chemistry classes, the master science faculty has one way to answer this question when learning about stoichiometry—calculating the quantities of reactants and products in a chemical reaction.

Chemistry teacher Ryan Zaremba revealed, “I use recipes as a model because the kids can easily relate to it. For instance, what happens when you run out of cheese when making grilled cheese sandwiches? You can’t make any more grilled cheese sandwiches. This simple concept applies to chemical reactions as well.” To instill this lesson, teachers led their charges through a eudiometer lab. Using the reaction between magnesium and red-dyed hydrochloric acid in a sealed tube (the eudiometer) to produce hydrogen gas, students can observe what happens when one of the reactants runs out: the reaction stops. “This lab was perfect for students to truly see chemistry,” teacher Kara Schupp said. “Chemicals mixing, reforming bonds and thus new compounds. Specifically, it was taking a piece of metal (Mg), mixing it with a liquid (hydrochloric acid) and creating a gas (hydrogen gas)!”

Next, the students quantify this process and use these measurements to perform a variety of stoichiometric calculations. Schupp explained, “Through the chemistry concept of stoichiometry, students can predict how much H2 gas will be produced (the theoretical yield), they can conduct the actual experiment to see how much hydrogen is actually produced (experimental yield), and they can thus calculate percent yield. They are able to use a new piece of lab equipment, the eudiometer, to collect and measure the gas created.” 

The practical nature of this activity and students’ ability to “see” the science happening before their eyes are key factors in the success of this experience. “Every year I am always impressed with the quality of the data we collect in this lab,” Zaremba noted. “Also, the kids like seeing the vigorous reaction take place and the ways their calculations add context and value to the concepts we have talked about in class.” Schupp added, “We have been talking about chemical reactions, types of reactions and balancing chemical reactions and only seeing it on paper, but now the chemical symbols, plus signs and arrows, limiting reactants, and words like ‘single replacement reactions’ come to life. Mg + 2HCl --> MgCl2 + H2!”

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