Group and periodic properties lab

Dan Shaffer
Melrose Area High School
Melrose, MN
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Summary

In chemistry lab, students will observe and perform experiments with the elements sodium, potassium, calcium, magnesium, sulfur and phosphorus. Conclusions will be made about trends down groups, across periods and relating to acidity/basicity of metal oxides vs. nonmetal oxides.

Learning Goals

  • Introduce students to elemental chemicals and their reactions
  • Introduce trends in periodic table
  • Challenge students to identify products in a chemical reaction

Context for Use

This lab was designed for advanced high school chemistry students (juniors or seniors) who can be trusted with small amounts of potentially hazardous chemicals. It can be used at any time when discussion of elements in the periodic table is desired. It's original design was later in the year as a fun introduction to a theoretical discussion of periodic properties after chemical reactions and chemical equations have been discussed.

Description and Teaching Materials

The elements sodium, potassium, calcium, magnesium, sulfur and phosphorus are reacted with water or oxygen in the air as appropriate by students and/or as a demonstration. Safety measures are taken to ensure proper use of the chemicals. Students are asked to make observations about reactivity and use these observations to derive group and periodic trends in reactivity. See attached lab handout for full details and teaching notes for setup and management notes. Lab instructions and teaching notes (Microsoft Word 41kB Aug15 08)

Teaching Notes and Tips

  • Fume hood is needed for combustion of sulfur and phosphorus. They both make a mess, so keep reusing the same spoon and plan on spending your lunch hour with the confligurating spoon in a Bunsen burner flame to remove excess gunk.
  • Chop the potassium and sodium in tiny chunks less than a small pea
  • Emphasize using a glass cover on the beaker immediately upon adding the potassium and sodium. Demonstrate this. Do not leave extra potassium or sodium around for the curious student to test too often.
  • Usually the mineral oil used to store potassium and sodium creates a bunch of smoke. Alert students that this is not part of the reaction.
  • Pound the calcium into a super thin strip to mimic the magnesium strip. Be prepared for flying chunks of calcium when you ignite it. It's far more violent than magnesium, but hard to get it thin enough to burn. A hammer on the black lab bench works well and keeps neighboring classes entertained.
  • Reemphasize to look away from the magnesium
  • Demonstrate anything that you feel is not appropriate for your students to do.
  • Find the Youtube video of Brainic's "alkali metals" to tie into this lab as a follow up when discussing it.
  • Expect that writing chemical equations for all reactions will create some difficulty. Note that for metals reacting with water that hydrogen gas and hydroxides are products.

Assessment

A student lab report is collected. Included is a table showing observations, proposed chemical equations for reactions, and proposed periodic and group trends in reactivity. The report is intended to be graded for thinking, not perfection in the chemical equations as some of these reactions are difficult to characterize.

Standards

Grade 9-12
II. PHYSICAL SCIENCE
B. Chemical Reactions: The student will describe chemical reactions and the factors that influence them
1. The student will describe chemical reactions using words and symbolic equations


This laboratory also addresses more advanced chemical concepts of periodic properties and acid/base applications. It extends past the scope of the Minnesota Academic Science Standards

References and Resources