Mystery Powder Analysis Gizmo Answer Key

Name: Allie Pollard Date: 04-20-2022 Student Exploration: Mystery Powder Analysis Vocabulary: Biuret solution, iodine solution, litmus paper, vinegar Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Prior Knowledge Questions (Do these BEFORE using the Gizmo.) A white powder is found spilled on the kitchen floor of a crime scene. A similar powder is found on the shoes of a suspect in the crime. 1. What are some powders that you might find on the kitchen floor? Sugar, salt, baking soda, flour. 2. How could you tell if the powder was salt, sugar, flour, or baking soda? If you had no other way of testing them, you could go by taste. Gizmo Warm-up The Mystery Powder Analysis Gizmo allows you to use a variety of tests to identify unknown substances. To start, drag the Baking soda test tube into the “Place tube here” area. 1. Under Appearance, click Test. Is baking soda a fine powder (no visible grains), or is it coarse (visible grains)? There are no discernible granules in the powder. 2. Litmus paper is an indicator of acids and bases. Under Litmus test, click Test. Which of the following results occurred? (highlight the answer.) A. Both strips red (acid) C. One red, one blue strip (neutral) B. Both strips blue (base) 3. Some substances react with vinegar to produce carbon dioxide, visible as bubbles. Under Vinegar test, click Test. Does the vinegar bubble? Yes 4. The blue Biuret solution turns bright purple in the presence of proteins. Iodine solution turns dark purple in the presence of starch. Try each of these tests. Does baking soda contain protein? No Does baking soda contain starch? No Activity A: Get the Gizmo ready: Known substances ● Click Reset. ● Be sure the Known substances are selected. Question: What are the properties of baking powder, baking soda, corn starch, gelatin, and salt? 1. Collect data: Use the Gizmo to test the five known substances. Fill in the results below. Substance Appearance (coarse or fine?) Baking powder Baking Soda Corn Starch Gelatin Salt Fine Fine Fine Coarse Coarse Litmus (acid or base?) Neutral Base Neutral Acid Neutral Vinegar (bubbles?) Biuret (protein?) Iodine (starch?) Yes Yes No No No No No No Yes No Yes No Yes No No 2. Analyze: Look at the results of your tests. A. Which substance(s) are acids? Gelatin B. Which substance(s) are bases? Baking Powder, Baking Soda C. Which substance(s) react with vinegar? Baking Powder, Baking Soda D. Which substance(s) contain protein? Gelatin E. Which substance(s) contain starch? Corn Starch 3. Apply: Suppose you find a mystery powder. It is coarse in appearance, has a neutral pH, and does not react with vinegar, Biuret solution, or iodine. Of the five substances listed here, which is it most likely to be? Salt 4. Challenge: Baking powder is a combination of three substances. One is an acid salt, and the other two are other “known” substances in the Gizmo. What are these two substances? Baking Soda and Cornstarch Get the Gizmo ready: Activity B: Unknown substances ● Click Reset. ● Under Select a sample, choose Unknown. ● Check that the Standard mystery set is displayed. (If not, click Refresh or Reload on your browser.) Question: How can you identify unknown substances? 1. Identify: Test tubes 1-5 are all contain single substances. Run the five tests on these powders, and identify the substance in each tube. Sample Appearance Litmus Vinegar Biuret Iodine Substance 1 Fine Neutral No No Yes Cornstarch 2 Fine Base Yes No No Baking Soda 3 Coarse Neutral No No No Salt 4 Fine Neutral Yes No Yes Baking powder 5 Coarse Acid No Yes No Gelatin 2. Identify: Test tubes 6-10 all contain mixtures of two substances. Run the five tests on these powders, and identify the TWO substances in each tube. Sample Appearance Litmus Vinegar Biuret Iodine Substances 6 Coarse/fine Acid No Yes/no Yes Gelatin and cornstarch 7 Coarse/fine Neutral Yes Yes/no No Salt and baking soda 8 Coarse/fine Neutral Yes No Yes Salt and baking powder 9 Fine Base Yes No Yes 10 Coarse/fine Acid Yes Yes/no Yes Baking soda and cornstarch Gelatin and baking powder 3. Analyze: In the two-substance mixtures you have investigated so far, are there any situations where there is more than one correct answer? Explain. Number nine could be baking soda mixed with either baking powder or cornstarch. They are both fine and have starch present and no protein. 4. Challenge: Test tubes 11-15 all contain mixtures of three substances. Run the five tests on these powders, and identify the THREE substances in each tube. (Note: Sometimes there will be more than one possible answer.) Sample 11 12 13 14 15 Appearance Coarse/fine Coarse/fine Coarse/fine Fine Coarse/fine Litmus Acid Acid Neutral Base Acid Vinegar No Yes Biuret Yes/no Yes/no Yes No Yes No No Yes/no Iodine Substances Yes Gelatin, baking powder and baking soda Yes Gelatin, baking powder and cornstarch Yes Salt, baking powder and cornstarch Yes Baking powder, baking soda and cornstarch Yes Gelatin, cornstarch and salt 5. Analyze: Based on your experiences, answer the following. A. Why is it hard to tell if a mixture contains salt? Salt is neutral and doesn’t have protein, starch or react with vinegar, so there is nothing that really stands out to identify it. B. How can you tell if a sample contains baking soda and cornstarch or baking powder? All three are fine whereas gelatin and salt are coarse. 6. On your own: For further practice, click New sample. In this set, the contents of every tube is randomized. You may even find new substances you haven’t seen before. Record your observations and make hypotheses about the contents of each tube. Good luck! I'm unsure on what to do with this one. I was unable to locate the new sample.