Atoms, Elements, and the Periodic Table - Learning Services Home

Name Date ClassMystery MixtureLab PreviewDirections: Answer these questions before you begin the Lab.1. Explain why it is important to wear goggles while performing this experiment.Hands-On Activities2. What are the three tests that you will apply to each compound?You will encounter many compounds that look alike. For example, alaboratory stockroom is filled with white powders. It is important to knowwhat each is. In a kitchen, cornstarch, baking powder, and powdered sugarare compounds that look alike. To avoid mistaking one for another, you canlearn how to identify them. Different compounds can be identified by usingchemical tests. For example, some compounds react with certain liquids toproduce gases. Other combinations produce distinctive colors. Somecompounds have high melting points. Others have low melting points.Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Real-World QuestionHow can the compounds in an unknownmixture be identified by experimentation?Goals■ Test for the presence of certain compounds.■ Decide which of these compounds are presentin an unknown mixture.Materialstest tubes (4)cornstarchpowdered sugarbaking sodamystery mixturesmall scoops (3)dropper bottles (2)iodine solutionSafety Precautionswhite vinegarhot plate250-mL beakerwater (125 mL)test-tube holdersmall pie panWARNING: Use caution when handling hotobjects. Substances could stain or burn clothing.Be sure to point the test tube away from yourface and your classmates while heating.Procedure1. Record your results for each of the followingsteps in the data table on the next page.2. Place a small scoopful of cornstarch on thepie pan. Do the same for the sugar andbaking soda making separate piles. Add adrop of vinegar to each. Wash and dry thepan after you record your observations.3. Again, place a small scoopful of cornstarch,sugar, and baking soda on the pie pan. Adda drop of iodine solution to each one.Wash and dry the pan after you recordyour observations.4. Place a small scoopful of each compoundin a separate test tube. Hold the test tubewith the test-tube holder and with an ovenmitt. Gently heat the test tube in a beakerof boiling water on a hot plate.5. Follow steps 2 through 4 to test yourmystery mixture for each compound.Atoms, Elements, and the Periodic Table 7