Physical Science Chapter 1

Name: ______Date: ______Hr:_____ Physical Science – Unit 6 Lab – Separating Mixtures – PART I

Introduction: In this lab, you will be working with and investigating different mixtures. Based on your understanding of mixtures and physical properties of certain substances, you will be identifying the substances that are in the mixtures.

Materials: Sample Mixtures in large stock bottles tweezers Magnet Hot Plate 1 – 100 mL beaker Hand soap 1-150 mL beaker test tube scupula glass stirring rod microscopic slide

Instructor Note – remember to add sugar and/or salt to necessary mixtures Procedure: 1. You will be given a mixture that contains three of the following substances. It is your job to figure out what three substances are in your mixture. In order to do this, you will have to use information off of the graph below.

Physical Properties Table - Substance Color Is it State at room Density (in g/mL) Melting Point Soluble in water? magnetic? temperature (in ○C) Iron metallic Yes Solid 7.87 1,535 no

Sulfur Yellow No Solid 2.07 112.8 no

Polystyrene white No Solid 1.05 240 no (a type of Styrofoam) Sodium white No Solid 2.17 801 yes Chloride (table salt) Stearic white no Solid 0.94 69.6 no Acid Sugar white no solid 1.59 186 yes

2. Using one of the two beakers provided, obtain 1 spoonful of a sample mixture and write the letter of your sample in the data section. This is VERY important! If you do not, you will get this entire section wrong. 3. Place a magnet on the outside of the beaker, move the magnet up and down on the side of the beaker. Record your results in the data table. Did the magnet affect your mixture? 4. Fill the second beaker 2/3 full of water. 5. Add a squirt of handsoap to the water and swirl to make sure the flotation of any material is not due to the surface tension of the water. 6. Place a small scoop of the mixture into the water, and stir. Does any of the mixture float? Sink? Record your results on the data table. Remember, if a substance’s density is less than 1 g/ml, it will float in water and if its density is greater than 1 g/ml, it will sink. 7. Put a very, very small scoop of the sample mixture into a test tube. Fill the test tube 2/3 full of water. 8. Cap the top of the test tube with your thumb (none of the reagents are hazardous to the skin) and shake it well. Observe if any of the mixture has dissolved. (This is called going into solution or soluble). Does any of it appear to dissolve? Record your observations in the data section. 9. Place a VERY SMALL onto a microscopic slide. Using your finger, even out the mixture until it is just one layer of particles thick. 10. USING THE TWEEZERS, carefully, (the hot plate might still be hot from other lab groups using it) place the slide onto the hot plate and set the heat to medium-high. MAKE SURE THAT NONE OF THE MIXTURE IS DIRECTLY ON THE HOT PLATE. IF IT IS, USE A DAMP PAPER TOWEL TO WIPE IT OFF OR IT WILL SMELL! 11. Does any of your mixture melt? This might take 2-5 minutes for your hot plate to get hot enough. FYI – hot plates will only reach about 200 ◦C when turned up all the way high (which you are NOT doing). 12. Return any extra to the stock bottle. 13. Clean up all equipment when done.

Data: Sample Magnetic Flotation Solubility Melting Substance Substance Substance Mixture Point “A” “B” “C” Letter

Conclusion Questions: 1. What is the difference between a pure substance and a mixture?

2. Was the first mixture you worked with (some of you might have only worked with one) heterogeneous or homogenous? Why?

3. For the following scenarios, choose the ONE physical property being used to separate the mixture: density, solubility, phase change, size separation, boiling points. a. When Uranium is purified, gaseous uranium is passed through a series of filters. The larger U-238 atoms pass through the filters at a slower rate than the smaller U-235 atoms. The U-235 may be collected in an enriched form after many passes through the filters. The original mixtures of isotopes may be separated into purified samples of lighter and heavier forms.

b. When iron ore is extracted from the the earth, it is then heated to a liquid. Impurities in the molten iron float to the surface of the liquid and are removed. These impurities are called slag.

c. Pure octane is extracted from an ethanol-gasoline mixture by allowing the ethanol to boil off first, being left with octane only.

4. Let’s “pretend” that you are stranded on an island. As you know, when you look out at the ocean, you are staring at a huge homogeneous mixture of sodium chloride, water and other elements (even gold). But did you know that if you drank that water, you would die from dehydration. The saltwater would actually “suck out” any water that might still be in your cells and they would dehydrate. SO…… how do you survive? If you were able to recover the water only from the mixture, you would not die from dehydration. While staying on the island, you have learned how to make fire. a. Based on our notes, what separation technique could you use to separate the salt from the water and still RETAIN THE WATER?

b. What physical property of the substances within the mixture are you relying on?

c. Get creative, in a single paragraph tell me exactly how you might carry this out……remember, you are on a primitive island! (Draw a picture if you like)