Supports NGSS MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred and MS-PS1.B: Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants; the total number of each type of atom is conserved, and thus the mass does not change.
This lab provides students the chance to perform three easy yet effective chemical reactions that demonstrate the Law of Conservation of Mass. Detailed procedures are provided on the student lab sheet for each reaction, along with spaces for students to record masses, chemical names, observations of the reactants and products, and indications that chemical reactions have occurred (precipitate formation, color change, & gas production).
The chemicals needed include: potassium iodide solution (0.1 M), lead (II) nitrate solution (0.1 M), copper metal turning/ribbon, sulfur powder, Alka seltzer
Other necessary materials include: balances or scales to measure mass, small plastic vials, Bunsen burners, ring stands and test tube clamps, 200 x 25 mm (larger sized) test tubes with stoppers, Florence/bubble flasks, balloons
For the series of analysis questions at the end of the lab, students can look up the Law of Conservation of Mass and then make the connection between the Law and their lab data. Students will reflect on the indications of chemical changes that occurred during the lab, answer an application question involving an open versus closed system, and balance a relatively simple equation from the lab.
I set this lab up as three sets of each of the three stations so that there are 9 stations in total. Each station takes about 7 minutes to complete. With the reflection questions, this lab would take about one 40-minute class period. Teacher notes are included as well as an answer key. The file is also editable.
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