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Lesson Overview
In this activity students carry out a chemical reaction in which two reactants produce three products. Students determine by chemical tests that the solid product is not the same as the solid reactant. They also discover that mass apparently is not conserved in this reaction. (The aqueous acid solution, the liquid product of water, and the gaseous product, carbon dioxide, are not accounted for by mass; the water and gas are driven off.)
Student Ability Level and Grouping
This lesson is appropriate for high-school general chemistry students working in pairs.
Expected Student Background and Skills
Students should have already learned about atoms and molecules and their ability to interact (but do not necessarily need to know why they do so). This lab activity would best fit in with a discussion about chemical reactions. Students must also be able to work safely in a laboratory and know how to interpret procedural instructions. They should know how to use a balance to determine the mass of a substance.
Time and Materials Required
Student activities span three days—part of one class period to do the demonstration and set the stage for the experiment, one class period to set up the reaction, overnight to dry the product, and the next day’s class to weigh the dry product, test the reactant and the product, collect data, and confer with partners.
The pre-lab demonstration requires approximately 15 minutes, preferably the day before the actual experiment begins, to allow the full class period for each subsequent part of the activity. The materials required are
- Magnesium ribbon
- Bunsen burner
- Striker
- Tongs
The lab activity requires two class periods, as detailed above. The materials required are
- 2.5 grams of sodium hydrogen carbonate (baking soda, NaHCO3)
- 5 to 6 mL of 6 M hydrochloric acid, HCl
- Several drops of 0.5 M silver nitrate (AgNO3) solution in small (15- to 60-mL) dropper bottle
- Evaporating dish (ceramic), small jar or beaker (100-mL maximum capacity)
- 3 test tubes, 13 x 100-mm with stoppers
- Medicine dropper or Beral pipette, long enough to reach down into the acid solution
- Goggles, gloves (if available), and lab apron (if available)
- Balance
Learning Objectives
After completing this activity, students should
- know how to synthesize a compound; and
- learn some basic tests to determine that the new substances (products) are different from the starting chemicals (reactants).
National Science Education Standards
Science as Inquiry
- Abilities necessary to do scientific inquiry
- Understandings about scientific inquiry
Physical Science
- Structure and properties of matter
- Chemical reactions
History and Nature of Science
- Nature of scientific knowledge
- Historical perspectives
Classroom activities are provided through the generous support of the Biogen Idec Foundation.