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Mystery Powders

based on 8 ratings
Author: Muriel Gerhard

Grade Level: 4th - 6th; Type: Chemistry

Objective:

Identify a variety of unknown substances that look alike by identifying their properties.

Research Questions:

  • What are properties?
  • What are physical properties?
  • What are chemical properties?
  • Define soluble, insoluble.
  • Define precipitate?
  • Differentiate between a physical and a chemical change?

On the information level, this experiment serves to acquaint students with the use of known properties to identify specific substances. For example, one can readily differentiate between salt and sugar by taste. One may differentiate these same substances by the appearance of the granules. Another approach would be to test them in terms of their solubility or insolubility in water. Still another approach may deal with chemical indicators. In sum, the student uses basic information such as the physical and chemical characteristics of substances in order to identifyt hem. In the process, the student develops basic laboratory skills in safely handling mystery ”substances .“ An exciting challenge!

Materials:

  • 5 plastic vials with covers
  • granulated sugar
  • salt
  • baking powder
  • flour
  • plaster of Paris
  • clear iodine
  • a beaker
  • water
  • 5 large plastic coated paper plates
  • a pen
  • 5 plastic spoons
  • 5 stirring rods
  • 5 small paper cups
  • magnifying glass
  • water
  • paper towels

These materials are readily available from the local supermarket and from the science classroom or purchased from Chem. Scientific or Science Kit.

Experimental Procedure:

  1. Gather all the materials you will need for this project.
  2. Wear your safety glasses, gloves and apron.
  3. Label each of plastic vials as follows, one each of A, B, C, D and E.
  4. Have a friend or a parent, fill each of the plastic containers with each of the white powders, namely salt, sugar, flour, baking soda and plaster of Paris. They are not to tell you into which of the five vials they have placed the powders. They are Mystery Powders to you!
  5. Your task is to identify each one by their properties, physical and chemical.
  6. Before you begin, copy the data chart provided below so that you can readily record your observations. You may wish to take photos of the reactions of each of the five white powders to display with your project or enclose in your final report.
  7. Start by placing 5 circles on the first large plastic plate and label them A, B, C, D and E. Now using separate plastic spoons, place a small amount of each powder in each circle. View each of the powders with your magnifying glass and record your observations. Note the size and shape of the particles.
  8. Be careful. Smell each of the powder. Any distinct odor? Record your observations.
  9. No tasting! One or more may be poisons!
  10. Now taking one powder at a time, place a small amount in a test tube and add water?  Stir. Use a separate stirring rod for each powder! Which ones are soluble in water giving you a clear solution? Which ones give you a cloudy or murky appearance? Record your observations in your data chart.
  11. Take a fresh plate, make your five circles, place each of the powders in the labeled circles and place a drop of iodine on each one. Any color changes? Record your observations.
  12. Repeat step 11, use afresh paper plate, but this time place a few drops of vinegar on each of the powders. Record your observations.
  13. Take each of the small paper cups. Place a teaspoon of powder in each one.  Use a separate teaspoon each time. Label the cups. Now pour a small amount of water on top of each powder and store the open cups for one day. Then observe and record your results.
  14. Based on the data gathered can you identify which of the white powders were sugar, salt, flour, baking powder and plaster of Paris?
  15. Write up your report. You may wish to include photos of the reactions. Be sure to include your bibliography.
Terms/Concepts: physical properties; chemical properties; physical change; chemical change; soluble / insoluble; precipitate; chemical indicators

References:

  • Masterton, W, Slowinski, E, Walford, E, Chemistry, Holt, Rinehart and Winston, New York, 1980
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