Mystery Substance Laboratory Experiment

Transcription

1 Mystery Substance Laboratory Experiment Name: 5 th Grade PSI Science Score: / 5 Experiment Question: How effectively can you determine what a mystery substance is by testing its observable properties? Hypothesis Starters: 1. How are a penny and a sugar cube different based on their observable properties? Explain your thinking. 2. How could you tell the difference between powders of sugar and chalk without tasting them? Explain your thinking. 3. Which substance is the most different from the other two based on its observable properties: sand, salt, or sugar? Explain your thinking. Purpose: In this experiment, you will identify one or more mystery substances based on their observable properties. Substances are often similar, for example salt and sugar can both be white powders that dissolve in water. Often they have small differences that can be easily observed in the laboratory. Salt will conduct electricity when dissolved in water. Sugar will not. You will be testing the following properties for each substance: 1. Color What color is the substance?

2 2. Shininess Is it reflective or dull? 3. Electric Conductivity Solid Does the substance conduct electricity as a solid? 4. Hardness How easy is it to break into pieces? 5. Magnetism Does the substance react to a magnet? 6. Solubility in Water Does the substance dissolve in water? 7. Electric Conductivity Solution Does the substance conduct electricity when dissolved in water? Safety: Do not taste any of the substances in this experiment. Be careful to keep the conductivity tester dry. Materials The following materials are needed to complete the testing: Procedure - goggles - apron - hammer - magnet - beaker - stirring rod - conductivity tester - plastic bag - sample substances for testing - distilled water For each of the samples record the following data below on the data sheets. 1. Color What color is the substance? Record the color of the substance. Be descriptive. If it is more than one color, list all that you observe or the pattern. 2. Shininess Does it reflect light? Does the object look shiny like a mirror or dull like chalk dust? 3. Conductivity as a Solid Does it conduct electricity? Touch both ends of the conductivity tester to a single piece of the substance. Does the tester light up or not? 4. Hardness Does it break into pieces? Tap the object lightly with a hammer. a. If the object did not break, ask your teacher for permission to hit it with more force and record your results. 5. Magnetic Is the substance attracted to a magnet? a. Place a small amount of the sample in a beaker. (Use the broken bit from the hardness test). Hold the magnet under the beaker and move it around slowly. Do the pieces move with the magnet? 6. Solubility in Water Does the object dissolve? Add some water to the sample in the beaker you used during the magnetism test and stir.

3 7. Conductivity in Water Does it conduct electricity? Test your mixture from the solubility test with the conductivity tester. Does the tester light up or not? 8. Repeat steps 1-8 for each sample Laboratory Questions: On a sheet of paper or in your laboratory notebook, answer the following questions for each station you were able to test. 1. Compare your results to the substances listed on the Suspect List to figure out what your mystery substances are. 2. If any of your results could be more than one substance, explain which substance you think each is and why. 3. What other tests would have been helpful in determining the mystery substances? Explain your thinking. Conclusion: On a sheet of paper or in your laboratory notebook, write a paragraph that summarizes the experiment results and covers the following key points. 1. Explain how many of your mystery substances you were able to identify and what they were. 2. If you could not identify one or more of the substances, explain why you could not do so.

4 Data Sheet Name

5 Notes to the Teacher: This could be set up as a station experiment where the students perform each station or as a demonstration experiment where the teacher performs each for the class as a whole. It is recommended that the teacher guide the students through the proper way to test each of the properties. In a forty-minute class period, most students should be able to successfully test at least five or six different samples. Having more samples available is ideal because then students may continue to test until the time is up. Also, students do not all need to start with the same sample. If there are five groups and fifteen possible samples, consider having group one start with sample one, group two starting with sample four, group three starting with sample seven, and so on. If this is the case, save time so that the students may all contribute their results to the class set of data for comparison purposes. This progression is meant to help save as much time as possible by having each test help prepare the sample for following tests. By starting with the physical observations, testing conductivity, and then testing hardness, if the sample breaks into pieces, those pieces should respond more visibly to the magnet and should be easier to dissolve in water if they will dissolve. The solution can then be used to test for conductivity in water. It may be helpful to have electrical leads, commonly known as gator clips for the conductivity tests of the solid substances. The leads may make it easier to have a good contact for purposes of completing the circuit. Keep in mind that regular tap water often conducts electricity without adding anything to it. As a result, distilled or deionized water is recommended. One tip for handling the magnet is to have it inside a plastic bag or to have the sample in the beaker with the magnet underneath. By keeping something between the sample and the magnet, the sample particles do not get stuck to the magnet itself. If you ve ever tried to clean iron filings off from a magnet, you know how frustrating that can be. Please see the suspect results list for possible chemicals. If students are only given one unknown, it should most likely be one of the white powders since they require several tests to determine. If the students are given multiple unknowns, one of the metals, at least one of the white powders, and one of the colored powders are recommended. If students are being given a substance not on the suspect list, be sure to add the substance to the list before distributing it to students.