Name: Date: Period: Identifying & Analyzing Powders Lab [Adapted from

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1 Name: Date: Period: Identifying & Analyzing Powders Lab [Adapted from ] In this lab, you will be observing physical and chemical properties of four different powders. Then you will use the physical and chemical properties that you observe to distinguish unknown mixtures of powders. Purpose To identify several household items by their physical and chemical properties To analyze mixtures of common household items of unknown composition To practice measuring matter and converting units To practice scientific writing Content Covered Describing and measuring matter Physical & chemical properties States of matter Introduction Part of the fun of chemistry is being able to identify different substances by tests. To identify substances, chemists use reagents which are known chemicals or mixtures of chemicals. When a reagent is added to a sample being tested, it may or it may not produce an observable change. Both the positive and the negative result will help identify the unknown sample being tested. In this simple system of common household chemicals, four powders and three liquid reagents are used: POWDERS: A: Baking Soda B: Corn Starch C: Alka Seltzer D: Table Salt LIQUID REAGENTS: I: White Vinegar II: Iodine Tincture III: Distilled Water A series of tests will be performed that will help you to find out how each of the powders behaves when the liquid reagent is added. When performing the tests, look for both POSITIVE RESULTS (chemical changes like color changes and the production of gas bubbles) as well as NEGATIVE RESULTS (no chemical change/no observable change) since both positive and negative results carry the same significance in chemical analysis. After you establish the tests that identify or indicate a difference between the four powders, you will analyze three samples of unknown composition: Two of your unknown samples will be mixtures of two powders (identified with a number between 10-99) One unknown sample will be a mixture of three powders (identified with a number between ). 1

2 Materials 2 grams of Baking soda 5 grams of Cornstarch 1 tablet of Alka-Seltzer 2 grams of Table Salt 4 ml of White Vinegar 4 ml of Tinctured Iodine 4 ml of Water 2 spot plates 3 pipets 3 test tubes labeled White Vinegar, Tinctured Iodine and Water 4 cups labeled Baking Soda, Cornstarch, Alkaseltzer, Table Salt 3 spoons 1 balance 3 unknown samples Procedure PART 1: IDENTIFICATION 1.) Write down 2 physical properties for each of the four powders and the three liquid reagents. Record the information in the data section. 2.) Weigh out 2 grams of table salt, 5 grams of cornstarch and 2 grams of baking soda. Record the actual weight of baking soda, cornstarch and table salt that you used and record the information in the data section. 3.) Break an Alkaseltzer tablet into two halves. Weigh the half of Alkaseltzer that you use in grams. Grind one half of the tablet into a powder. Use the bottom of your spoon to grind it up in a cup 4.) Place small amounts (use a spoon) of the four powers in each of the 12 depressions of your spot plate as show in the diagram below. 5.) Samples of white vinegar, iodine tincture and water have been placed for you into three clean test tubes. Make sure that the test tubes are labeled. Put a pipet into each of the test tubes. Throughout the experiment, make sure that the same pipet is always used for the same liquid reagent. 6.) To each of the 12 solid samples in the spot plate, add a few drops of the three liquid reagents according to the diagram below. 2

3 7.) Record your observations and briefly describe how you can identify each powder. PART 2: ANALYSIS 1.) Check out your three unknown mixtures and record their numbers below and in the table in #2. Unknown #1: (2 powders) Unknown #2: (2 powders) Unknown #3: (3 powders) 2.) Test the unknown sample with each of the three liquid reagents as you did in Part 1. Follow the diagram below when arranging the chemicals in your spot plate. White vinegar Unknown1 # Unknown2 # Unknown3 # empty Iodine tincture Unknown1 # Unknown2 # Unknown3 # empty Distilled water Unknown1 # Unknown2 # Unknown3 # empty 3.) State the composition of each mixture. 3

4 Data & Observations PART 1: IDENTIFICATION 1. ) Physical Properties Record at least 2 physical properties for each powder and for each liquid reagent. Powder/Reagent Physical Properties Baking Soda Cornstarch Alka-Seltzer Table Salt White Vinegar Tinctured Iodine Water 2.) Measurements Record the mass of the four powders that you used in this lab. Make sure you take significant figures into consideration. Powders Mass Baking Soda Cornstarch Alka-Seltzer Table Salt Here s the volume of the three liquid reagents that you used in this lab. Make sure you take significant figures into consideration. Reagents Volume White Vinegar Tinctured Iodine Water 4 ml 4 ml 4 ml 4

5 3.) Results Record what happened in each spot when you mixed the powders. Was there a chemical change? How do you know? Baking Soda Cornstarch Alka-Seltzer Table Salt White Vinegar Tinctured Iodine Water 4.) Conclusion Briefly describe how you can identify each powder using the results you got from this lab. Powder How can I identify this powder? Baking Soda Cornstarch Alka-Seltzer Table Salt 5

6 PART 2: ANALYSIS In this section, you will report the data you got when you tested the unknown samples. You will also analyze your results to figure out what powders are in each sample. 1.) Report your unknown numbers Two-power mixture #1 Two-powder mixture #2 Three-powder mixture 2.) Results Unknown #1 (2 powders) Unknown #2 (2 powders) Unknown #3 (3 powders) White Vinegar Tinctured Iodine Water 3.) Conclusion 1.) Write down what you think powders each unknown contains. Unknown #1 and #2 (with a 2-digit number) contains only 2 powders. Unknown #3 (with a 3-digit number) contains only 3 powders. a.) Unknown #1 : I think Unknown #1 contains and because. 6

7 b.) Unknown #2 : I think Unknown #1 contains and because. c.) Unknown #3 : I think Unknown #1 contains,, and because. 2.) What is matter and how do we know that the materials (the powders and the reagents) we used in this lab were matter? 3.) In this lab, we measured the mass of our powders in grams (g). Convert the mass of your baking soda sample to kilograms (kg). Show the math work you did for this conversion below. 4.) In this lab, we measured the volume of our liquids to be 4 milliliters (ml). Convert this measurement to liters (L). Show the math work you did for this conversions. 5.) In this lab, you recorded the mass each powder. In this table below, write each measurement in scientific notation also. Baking Soda Cornstarch Alka-Seltzer Table Salt Powders Recorded Mass Scientific Notation 7

8 6.) We saw all three states of matter in this lab. Name examples of where you saw solids, liquids and gases in this experiment. 7.) What are physical properties and how did we use them in this lab? Why are they useful in science and in describing matter? 8.) We saw chemical changes in this lab. What types of chemical changes did you see and when did you see these chemical changes happen? 9.) Explain in a paragraph how you figured out what unknown1, unknown 2 and unknown 3 were. 8