25.1 DISPOSING OF TOXIC HEAVY METALS PRE-LAB: PART A- “FIXING” THE COPPER IONS IN A SOLID MIXTURE

LESSON TARGETS I can understand that many useful chemical processes produce waste by-products that must be disposed of safely. I can experiment with different products to find the best method to solidify and safely dispose of the liquid waste produced during the refining process.

VOCABULARY Leach- the removal of a substance by the filtering of water or other liquid (ex. Rainwater can leach minerals and fertilizers from soil.) Heavy metals- metal of relatively high density, or of high relative atomic weight. Excessive levels of exposure can be damaging to humans.

TESTABLE QUESTION How does the fixing of copper sulfate in different concentrations of cement or sodium silicate affect the leaching of copper from the solid material? Note: We want the copper to stay in the solid material. This would mean we are keeping it out of the soil and water…

HYPOTHESIS Write a hypothesis for what you believe will happen with the copper when it is fixed into a solid material. If the copper sulfate is combined with ______________ then it will _____________, because______________________.

MATERIALS List the materials you will use in Part A make sure your list is bulleted. 180mL bottle of sodium silicate Portland cement 120mL dropper bottle of 50,000ppm copper sulfate sln. Clear plastic cup Plastic spoon 30mL graduated cup Safety glasses Paper towels

SAFETY NOTE Portland cement can irritate your eyes and lungs. Do not breathe in the mixture and wear your goggles. Sodium silicate is a skin irritant; wash thoroughly if it comes in contact with your skin.

VARIABLES Manipulated Variable: Ratio of cement to sodium silicate Responding Variable: The concentration of copper sulfate Control Variables: Amount of copper sulfate; time to solidify

PROCEDURES PART A 1.Pour measured amount of Portland cement into the clear plastic cup. Use a paper towel to wipe out any dry cement that clings to the side of the cup. 2.Add 10mL of 50,000ppm copper sulfate sln. to the cement in the plastic cup. Stir to combine. Rinse the graduated cup. 3.Use the graduated cup to add the assigned amount of sodium silicate to the copper-cement mixture. Mix well. Record description of mixture in data table. 4.Label cup with period and group number. 5.Place in fume hood to dry overnight.

DATA TABLE Check with other groups and fill in the information for the “Appearance of Mixture”. Look in the Fume Hood to see the dry mixtures.

PART B LESSON TARGET I can calculate the concentration of a waste solution based on the concentration of a known solution.

PART B. CONTNTINUED 1.Add 10 drops of your teams copper sulfate sln. to Cup 1 2.Add 9 drops of water to Cups 2- 5, and 10 drops of water to Cup 6. 3.Transfer one drop of sln from Cup 1 to Cup2. 4.Continue dilution procedure adding one drop of the previous sln. to the next cup up to Cup 5. 5.Record the color of each cup in your data table. 6.Add 10 drops of ammonia to all 6 cups. 7.Record observations.

SERIAL DILUTION PART B 50,000ppm Sln. OR 24.1 Waste Sln.

PART B. ANALYSIS QUESTIONS 1.How does the addition of ammonia help determine the concentration of copper in a solution? Is it necessary? 2.What is the lowest concentration of copper that can be detected using the ammonia test? 3.Compare your groups estimate of the concentration of copper in the undiluted waste solution from activity 24.1 (Part A, Procedure step 9) with the estimate made by another team. How close are the two estimates? Explain reasons you see for any variations. What do you think you should do if the variations are large?

PART B. ANALYSIS QUESTIONS 4.An independent laboratory performed the same test as Team A on a 50,000ppm copper sulfate solution. They report the data in the table shown below. Describe the similarities and differences between their results and those your group reported.

EXPERIMENTAL SET UP- BEFORE ADDITION OF AMMONIA

RESULTS These circles represent the experimental controls – Water and ammonia.

RESULTS What do the results suggest?

PART C TESTING YOUR SOLIDIFIED MIXTURE UNDER ACIDIC CONDITIONS Lesson Target I can determine if solidifying heavy metals in a solid matrix stops them from leaching into the surrounding environment.

PROCEDURES 1.Pick up a 5ml crushed sample of the solid you prepared in Part A. 2.Prepare a Filter set up- wetting the filter paper to help it sit in the funnel. 3.Add 10mL of simulated acid-rain solution to the crushed solid in your cup. Swirl for 30 seconds. 4.Transfer the contents of the cup to the filter set up and clean the cup. 5.Using the data table from Part A record the color of the filtrate collected in the large cup. 6.Transfer 10 drops of filtrate to Cup 1 of your tray, add 10 drops of 5% ammonia to it. Record the color in your table. 7.Estimate the copper concentration. Record in your table. 8.Complete your data table by checking with other groups.

ANALYSIS QUESTIONS Answer analysis Questions 1-5 in your lab notebook. 1.