Lab Modules from Dr. Susan B. Piepho Susan Piepho's Websites Department of Chemistry Sweet Briar College Sweet Briar, Virginia 24595

All of us have an amazing arsenal of chemicals in our homes. To see this simply venture into your kitchen, laundry, bathroom, shop, garden shed, or garage, and begin reading labels! In this experiment students take a close look at these chemicals - specifically cleaning products. Chemical properties of these products are investigated during the first week of the lab. A wide variety of chemical concepts are brought into these investigations including solubility, pH, fluorescence, emulsification, water-softening, and oxidation-reduction. Each student pair first does short experiments in each area, and then designs and completes a study of its own choosing. In the second week the class carries out controlled experiments in stain removal. Working in groups, students simulate washing machines, automatic dishwashers, and test abrasives. These experiments introduce students to the concept of a controlled experiment. Groups pool their data and arrive at conclusions useful to them as consumers; e.g. the washing machine group decides on the best cleaning conditions for the set of fabrics and stains tested. The lab ends with oral reports by the groups summarizing the results of the controlled experiments in stain removal and oral reports by each pair giving the results of the independent investigations done the first week.

The experiment works well in either a general chemistry laboratory course for science students or in a laboratory course for liberal arts students. It may be used in either the second half of the first semester, or in the second semester. The more background the students bring to the experiment, the more they get out of it, and the more sophisticated their self-designed experiments.

†Professor of Chemistry, Sweet Briar College: author to which correspondence should be addressed.

This experiment places the student in the role of a drug investigator. Identification of a white powder (an over-the-counter medication or a look-alike powder such as cornstarch) is carried out with the aid of preliminary qualitative tests, thin layer chromatography (TLC), and Fourier Transform Infrared Spectroscopy (FT-IR). Each pair of students is given two knowns and two unknowns. During the first week they perform a series of preliminary tests and use the class results for the knowns to narrow down possibilities for their unknowns; they then do TLC or run the FT-IR of their samples. During the second week of the lab the TLC and the FT-IR groups reverse. Students compare the data for their unknowns with class data for the knowns and attempt to make a positive identifications. To make things more challenging a few "wild card" unknowns are included which don't correspond to any of the knowns tested by the class.

The lab introduces students to the immense power of a modern spectroscopic technique, FT-IR. An added benefit of the experiment is that they learn about the virtual identity between generic drugs and the equivalent brand-name products - a good lesson in consumer chemistry!

The experiment works well in either a general chemistry laboratory course for science students or in a laboratory course for liberal arts students. It may be used in either the second half of the first semester, or in the second semester. The more background the students bring to the experiment, the more they get out of it. The experiment also may be used in an organic chemistry laboratory, but in that case the chemical structures of the drugs should be discussed and students should be encouraged to look for functional group peaks in their FT-IR spectra.

†Professor of Chemistry, Sweet Briar College: author to which correspondence should be addressed.

Everyone is spellbound by a fire, especially a large destructive one. Suppose it is your job to help in the investigation of such a fire. What evidence should you collect, and how do your prove (or disprove) arson?

This module introduces students to one of the tools of the arson investigator - the gas chromatograph (GC). During the first week of the lab, chromatograms are obtained for a number of commonly available hydrocarbons and petroleum products which could be used to start a fire. Once the class has obtained GC data on all of the knowns, students are given an unknown to identify which mimics some of the features of real samples collected during an arson investigation.

During the second week of the lab, the challenge is to try to identify some of the organic chemicals which give rise to the different peaks in the GC spectra. The GC of selected pure organic liquids are run under identical conditions to those used on the "arson" samples, and retention times are compared. (If a GC with a mass spectrograph (MS) detector is available, GC/MS data could be substituted for this part.)

All samples are run in the gas phase using gas-tight syringes. The head space vapor (the vapor that collects over a sample that has equilibrated in a sealed container) is injected into the GC. The big advantage of vapor samples is that they require much shorter run times and yet still give excellent data for volatile samples.

The module is suitable for a wide range of courses including liberal arts chemistry and general chemistry. It serves as a good introduction to gas chromatography in organic chemistry or analytical chemistry laboratories.

†Professor of Chemistry, Sweet Briar College: author to which correspondence should be addressed.

Chemical separation and analysis is based on an understanding of equilibria. One of the more difficult concepts to teach students is the understanding of how salts react with added reagents, and how their reactivity (or lack of it) may be made to work to the advantage of the chemist. In this lab students explore the chemistry of five transition metal ions: Cr³⁺, Fe³⁺, Ni²⁺, Cu²⁺, and Ag⁺. The reactivity of the cations with NaOH, NH₃, HCl and HNO₃, both alone and in combination, is first explored. In the process students investigate complex ion formation and amphoterism. Next the selective precipitation of the cations as sulfides is investigated. Students then run confirmation tests on the cations.

Once students have explored the reactions outlined above, they are asked to develop a separation scheme for a set of three of the cations and then to test it in the laboratory. Students in each pair are assigned complementary three-cation sets so that, between the two students, all five cations are included. Once the pair's three-cation schemes have been successfully demonstrated in the lab, the pair is challenged to develop a separation scheme for the complete set of five cations. They then test out their five-cation scheme.

The lab might not appear especially difficult, but it is tremendously rich in concepts. For most groups of general chemistry students it is best taken up in a fashion that will appear leisurely to the instructor. It is amazing how few students recognize when they have a precipitate (especially if it is at all milky or gelatinous), understand that both NH₃ and NaOH typically give the same hydroxide precipitates, know instinctively that a strong acid usually dissolves a hydroxide precipitate, have a feel for complex ion formation, or can readily understand the selective precipitation of sulfides based on pH!

While nearly all mainstream general chemistry classes teach these concepts in considerable detail by the middle of the second term, the students do not digest them easily. Thus typical Group I, II, etc., qualitative analysis labs are handled in cookbook fashion by students. What this module aims to do is to first let the students experiment with the basic concepts, one-at-a-time. Once these have been digested, they are asked to put them to work in a separation scheme of their own design. One nice feature is that there are a number of ways the separations may be accomplished, so there is no single right answer.

For most student groups, the module is best used as a three week lab. Here we assume that students will answer the questions posed in the lab module as they proceed through the experiment. It should be placed around the middle of the second semester of a typical science-sequence course in general chemistry. Instructors will appreciate the clear discussion of the concepts given in the module, and the opportunity for their students to master them in a creative format. Any extra time left over in the third week may be used for individual investigations designed by the student pairs. Ideas for such projects are given in the module.

†Professor of Chemistry, Sweet Briar College: author to which correspondence should be addressed.

Most of us don't think about it much, but there is science behind the way food is cooked, the equipment used in its preparation, and our current understanding of nutrition. In this experiment three quite different facets of culinary chemistry are explored: (1) how microwave ovens and conventional ovens work, (2) the principles behind sauce making, and (3) the relative loss of vitamin C using three different methods of cooking broccoli. The real-world connection of this laboratory shows students the relevance of chemistry to their lives.

The module may be used as a one, two, or three week lab. Parts (1) and (2) may be done in one week with students working in pairs. The interaction of electromagnetic radiation with matter is the key concept in Part (1), while Part (2) involves the chemistry of starch. Students are big users of microwave ovens and are eager to learn how they work. Part (3) works well as a one-week lab with students working individually and pooling data. The experiment, which involves the titration of Vitamin C with I2, is an interesting way to introduce students to the titration procedure: no prior experience with titration is assumed. Concepts include titration, oxidation-reduction reactions, the role of vitamins, and nutrition. The results are of great interest to today's nutritionally conscious students.

If a three-week sequence can be scheduled, we recommend that the third week be devoted to individual investigations designed by each student pair. The numerous suggestions for further research given in the module should stimulate ideas for these short projects.

The module is appropriate for the first semester in either a general chemistry laboratory course for science students or in a laboratory course for liberal arts students. Part (1) fits in well with the discussion of electromagnetic radiation which comes early in the first semester in most introductory courses. The calculations in Part (3) are simple enough that the experiment may be done early in the term. Part (2) is self-contained and may be placed as convenient.

†Professor of Chemistry, Sweet Briar College: author to which correspondence should be addressed.

Those who live in the Rust Belt are daily aware of the ravages of time, water, and salt - as are those who live near the oceans. Electrochemistry ruins our cars, destroys our bicycles, and generally makes life a constant Nernst equation. At the same time we look to electrochemistry for cleaner, safer forms of energy which can have broad uses, from the fuel cells of space shuttles to rechargeable batteries and the tiny batteries in watches and hearing aids.

The first three sections of this laboratory module explore voltaic cells, corrosion, and electrolysis. Topics investigated include the effect of changes in concentration and cell makeup on potential of the voltaic cells, factors affecting the rate of corrosion, methods of preventing corrosion, and identifying the products of electrolysis reactions. The section on corrosion has lots of "real-world" applications. The final section is a team investigation.

The module is appropriate for general chemistry, liberal arts chemistry, or environmental chemistry laboratories. It correlates well with the electrochemistry topics taught towards the end of the second semester in typical general chemistry courses. Plenty of material is included in the module to challenge the better prepared students. This material can be skipped over, and questions related to it may be omitted, in lower-level chemistry laboratory courses; in these classes instructors may want to emphasize the section on corrosion.

The module may be completed in two three-hour labs. Voltaic cells and corrosion are investigated the first week. During the second week students explore electrolysis and do a team investigation.
^†Author to whom correspondence should be addressed.

The concepts of light and color transcend the boundaries of art, chemistry, biology, and physics, and influence our day to day lives in countless ways. In this module the concepts of light and color are examined, both qualitatively and quantitatively, and the basic science behind some everyday observations is explored. Topics investigated include the use of diffraction gratings, the line spectra of atoms, determination of the wavelength of a Helium-Neon laser, flame spectra, the use of Beer's Law, the absorption spectrum of colored dyes, and additive, subtractive, and complementary colors.

The lab correlates well with topics studied in the first semester of typical general chemistry courses. It is also appropriate for liberal arts chemistry courses. The module contains 10 parts and requires two three-hour laboratory periods for completion. The last section of the module is a self-designed team investigation.

^†Author to whom correspondence should be addressed.

As a result of water's unique physical properties, the evolution and maintenance of life on this planet depends heavily on the presence of appropriately pure water. Human beings can survive extended periods of time with no food but only a few days without water.

In this module students test water samples from local lakes and/or water supplies. Tests include conductivity, dissolved oxygen, pH, alkalinity, hardness, and turbidity. The module includes information on sampling techniques and the storage of water samples. It also includes a thorough discussion of the chemistry behind the methods used. Sample data is given in the instructor's notes.

The module is appropriate for general chemistry, liberal arts chemistry, environmental chemistry, or analytical chemistry laboratories. The lab experiments may be completed in two three-hour labs if students divide up the more lengthy tests and pool their data. Plenty of material is included in the module to challenge the better prepared students; this material can be skipped over, and questions related to it may be omitted, in lower-level chemistry laboratory courses.

^†Author to whom correspondence should be addressed.

Author Table

General Chemistry Organic Chemistry

Environmental Chemistry Liberal Arts Chemistry

Analytical Chemistry Upper Level Chemistry

Contact Professor Susan Piepho with feedback on her lab modules at piepho@sbc.edu