Atomic Absorption Determination of Zinc and Copper in a Multivitamin
Determination of Phosphorus Content in River Water
Experimenting with Copper (II) Solutions
Investigating a Sewage Lagoon
Investigating the Relationship between the Mass of a Liquid and its Volume
Measuring Nitrate by Cadmium Reduction
Shrinky Dink Palettes
The Aspirin Shelf-Life Scenario
Using Bottled Water as a Problem Solving Exercise in Chemical Identification
Atomic Absorption Determination of Zinc and Copper in a Multivitamin
Atomic absorption spectroscopy (AAS) is an important analytical technique based upon the absorption of radiation by free atoms. Virtually all metallic elements can be directly detected with excellent accuracy, precise quantitation, and very sensitive detection limits. This technique can also be used to indirectly detect and measure the amounts of some nonmetallic elements. Atomic absorption requires a surprisingly simple apparatus. Students compare the amount of zinc and copper listed on a vitamin bottle to the value obtained using AAS.
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Determination of Phosphorus Content in River Water
In this experiment,students discover that a pure sample can become contaminated during preparation for analysis. The students colorimetrically analyze water samples from a river for phosphorus. During the sample preparation,one group of students (Gila Laboratory) decolorizes the "murky " water with activated carbon,,while the other group (Graham Laboratory)decolorizes the water with activated carbon that has been acid washed. Activated carbon contains small amounts of phosphorus. Acid washing removes the phosphorus. The data is compared,and the students then try to determine why the results differed.
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Experimenting with Copper (II) Solutions
This experiment helps students determine that the relative concentration of copper ions in water can be determined by a color comparison. Students make a copper(II) sulfate solution of a given concentration. Students dilute their initial solutions until their solutions are colorless. Students work in groups of 3-4, comparing solutions to discover any relationship between color and concentration. A portion of each solution will be mixed with concentrated ammonia solution, forming a dark blue copper-ammonia complex. Students decide if the complex can be used to find the useful concentration of copper ions in a swimming pool water sample.
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Investigating a Sewage Lagoon
Sewage lagoon systems for treatment of wastewater, also called total containment ponds, are becoming an attractive, cost-effective alternative for single residences and small communities. A sewage lagoon system in a residential or small institutional setting usually consists of two ponds and a wetland area. Sewage is pumped into the first pond, where settling and some decomposition take place. Water flows through a pipe into a second pond where further decomposition takes place. It then flows into a wetlands area. In very wet weather, the wetlands area discharges into a creek. Using kits such as those produced by Hach, CHEMets, and LaMotte, students can investigate various analytes such as dissolved oxygen, phosphates, ammonia, and nitrates. In addition, they can investigate conditions such as temperature and pH. By comparing differences among the three areas of the system and/or changes in the system over time, students can assess the condition, progression, and effectiveness of the system.
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Investigating the Relationship between the Mass of a Liquid and its Volume
Students fill a buret with one of five liquids, note the initial volume, and mass an empty beaker. They then deliver a portion of the liquid into the beaker, note the buret reading, and mass the beaker with the liquid. This process is repeated nine more times, adding the liquid to that which is already in the beaker. Students share data for all five liquids. Using a spreadsheet program, the students enter the data for each liquid, plot a graph of mass vs. volume for each liquid, and obtain the slope, y-intercept, and R 2 regression value for each line. The students then draw conclusions, answer questions, and form hypotheses based on the data and spreadsheet analysis.
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Measuring Nitrate by Cadmium Reduction
In this experiment, each student is assigned the task of designing an experiment to evaluate the effects of various treatments on the nitrogen cycle in a freshwater aquarium. The students are required to maintain a laboratory notebook of all work, measure the key analytes of the bio-system at periodic intervals, analyze and interpret data through appropriate tables and graphs, and write a formal report at the end of the term. The students set up the experiment using small goldfish bowls and incorporate some treatment, for example, a freshwater plant. This arrangement might have a bowl with fish only, one with a plant only, one with fish plus plant, and one with neither plant nor fish. A variety of techniques for analyzing for nitrate and ammonia are included depending on the time available and level of sophistication desired. Since nitrite is typically not observed in this experiment, a technique for its determination is not included.
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Shrinky Dink Palettes
This activity is designed to provide practice for students using equations for finding wavelength, given values for energy and frequency (lv=c, E=hv, and l=ch/E). They then apply the results in a creative project to make key rings or earrings.
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The Aspirin Shelf-Life Scenario
This quantitative exercise is designed to give students experience using the Spec-20 in determining species concentration. It also allows the students to determine if salicylic acid is present in commercial aspirin and the amount that may be present as the aspirin decomposes. In the lab, students determine the proper wavelength to use in checking for salicylic acid concentration. They also create a known concentration curve for the colored complex. The students also develop a long-term testing program involving the type of packaging material used for the aspirin and the possible environmental storage procedures the consumer may use and their effect on the shelf-life of the aspirin.
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Using Bottled Water as a Problem Solving Exercise in Chemical Identification
In this exercise, students are divided into groups of two or three. The groups are given four unidentified bottled waters in unmarked containers and the chemical characteristics taken from the labels on the bottled waters. The students must devise and carry out a plan to match the water in the unmarked containers with the appropriate labels. This lab is appropriate after a discussion on water quality so that students have a basic knowledge of hardness, alkalinity, pH, metals, and nutrients found in unprocessed water. A typed proposal outlining the methods, chemicals, equipment, and instruments needed for analysis, with references, must be approved by the instructor before students analyze the samples. Students are coached on the appropriate methods without dictating exact procedures.
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| Mickey Sarquis | |
| mickey@terrificscience.org | |
| Terrific Science, Cincinnati, Ohio |