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Download WHAT CHEMISTS DO: INDEPENDENT LAB EXAM
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Name _____________________________________class______ WHAT CHEMISTS DO: INDEPENDENT LAB EXAM PURPOSE: To identify several common household chemicals by their chemical properties and to analyze a mystery mixture of those household chemicals to determine its ingredients. REASEARCH AND PRINCIPLES: Part of the fun and importance of chemistry is being able to identify different substances by tests. To identify substances, chemists use reagents. When a reagent is added to a sample being tested, it may or it may not produce an observable change, which can help identify the unknown sample being tested. PROCEDURES AND SUMMARY: You will perform a series of tests to help you to find out how each of the powders behaves when the liquid reagent is added. You will have four different powders to which you will add three different liquids one at a time to see if there is a reaction. When doing the tests, look for color changes, the production of gas bubbles, as well as no observable change - since any results will help you figure out what the substance is. After you complete the reaction tests you will analyze a mystery mixture and use what you have discovered about the separate powders to identify what is in them: (hint) EXPERIMENT: PART I: SET UP 1. Put you goggles on. Place three VERY SMALL amounts (use the metal scoops) of the four powders in each of the 12 dips of your chemplate as shown below. Be careful not to mix. Baking Soda Baking Powder Corn Starch Sugar Baking Soda Baking Powder Corn Starch Sugar Baking Soda Baking Powder Corn Starch Sugar 2. Now place droppers of each liquid along the side as shown below. Vinegar Baking Soda Baking Powder Corn Starch Sugar Iodine Baking Soda Baking Powder Corn Starch Sugar Water Baking Soda Baking Powder Corn Starch Sugar PART II: PROPERTIES OF THE POWDERS 3. You are ready to start testing for reactions that will help you identify the powders. Put a few drops of the vinegar in the baking soda and record what happens. Next add drops of vinegar to the baking powder and record what happens. Repeat this process with the next two powders. When you have finished observing and recording vinegar reacting with all four powders, do the same thing with the iodine and water recording your observations in the chart below. Look for color changes, gas bubbles, as well as no observable change. Baking Soda Baking Power Corn Starch Sugar Vinegar (clear) Iodine (brown) Water (clear) PART III: APPLICATION AND IDENTIFICATION 1. Using a CLEAN DRY chemplate get your mystery sample and add 3 scoops in to any row of the chemplate. 2. Test the unknown sample with each of the three liquid reagents in the same manner as it was done in Part I. Record the result of your tests below. Mystery Mixture Reactions White Vinegar Iodine Tincture Distilled Water CONCLUSION: Compare the reactions of the mystery powder to your properties tests from part II. Find matches to determine what powders are in the mystery mix. The mystery mixture contains: ________________________________________________________ How can identifying unknown materials be helpful to us in the real world? _________________________________________________________________________________ _________________________________________________________________________________ CLEAN UP: Clean your station so it is exactly as it was before you started the lab.
