Mr. Mott. Polar/Nonpolar and Water Lab. Introduction:

Transcription

1 AP Biology Mr. Mott (source: Mrs. Miriello) Polar/Nonpolar and Water Lab Name Class Period Introduction: Solutions are homogeneous mixtures comprised of a solute (the dissolved substances) mixed in a solvent (what it is dissolved in). Homogeneous solutions are evenly distributed meaning that when observing, it all "looks" the same. A glass of tea is an example of a homogeneous solution. In living systems water is considered the universal solvent. Solutions are physical combinations, not chemical combinations. As we discussed in class, there are two types of covalent bonds, polar and nonpolar. Molecules joined by polar covalent bonds are not "sharing" the electrons evenly and will have resulting areas of partial charge around different areas of the molecule. Molecules joined by nonpolar covalent bonds are "sharing" the electrons evenly and will not have areas of partial charge around the molecule. Ions are single atoms or groups of atoms that have gained or lost electrons and now have a resulting charge. This information is important in understanding how solutes and solvents will combine. This lab explores the interaction of various solvents and solutes related to the specific characteristics of their bonds. We will be looking at two different types of crystal solids and two types of liquid solvents. While we are investigating physical "mixtures", the chemical nature of the solvent and solute will impact the resulting solution. This lab also investigates various properties of water (polar) and nonpolar substances. Follow the directions of the lab and write your observations on this sheet. Be very specific and detailed with your observations. They will help you answer the analysis questions.

2 Part A. Interactions of two different types of crystal solids and two different types of liquid solvents. Materials: 5 test tubes - labeled #1 through #5 stoppers Copper Chloride Iodine - poisonous and can cause sever burns this remains on teacher front desk! Water Substance X Spatula Graduated cylinder China Marking Pencil Procedure: 1. In test tube #1 - Using a spatula, add a FEW crystals of copper chloride to 3ml of water in a test tube. Stopper the tube and shake vigorously. Does the copper chloride dissolve in water? Explain what you see. 2. In test tube #2 - Add a few crystals of Iodine with a spatula to 3ml of water in a second test tube. Be careful of the Iodine! Stopper the test tube and shake it up. Does the iodine readily dissolve in the water? Explain what you see. 3. In test tube # 3 - Add a few crystals of copper chloride to 3ml of Substance X. Stopper and shake well. Does the copper chloride dissolve in Substance X? Explain what you see. 4. In test tube # 4 - Add a few crystals of iodine to 3 ml of Substance X. Stopper and shake well. Does the iodine dissolve well in the substance? Explain what you see. 5. In test tube # 5 - Add 3 ml of Substance X. Then add the iodine water solution you prepared in test tube # 2. Pour the contents of test tube #2 into test tube #5. Stopper and shake well. Describe the results.

3 6. Pour the contents of test tube #1 into test tube #4. Stopper and shake well. Describe your results. 7. Now add ten drops of detergent to test tube #4 which contains the combination of test tubes #1 and #4. Stopper and shake well. Do the two liquids separate as before? Describe what you see. Part A. s - Study your data that you have recorded concerning the solvents and solutes that you combined above. Think about the nature of the bonds that specific to each of the solvents and solutes as you answer the following questions. We will discuss all of the results and this information should be used to help answer the questions. 1.Which solute, copper chloride or iodine can dissolve in water and why? 2. Which solute, copper chloride or iodine can dissolve in substance X and why? 3. Which of the solutes used in this lab is nonpolar and WHY? 4. Which of the solvents used in this lab is nonpolar and WHY? 5. What did you do in step #5 and why did you get the results that you observed in step #5? 6. What did you do in step #6 and why did you get the results that you observed in step #6? 7. What did you do in step #7 and why did you get the results that you observed in step #7? 8. From what you observe in your daily life, do you predict that sugar is soluble in water and why? 9. From what you observe in your daily life, do you predict that sugar is soluble in Substance X and why?

4 Part B. Pennies Using the pennies and dropper provided - each team member should perform and compete at this activity. Compete with each other for "who can place the most drops of water on the penny WITHOUT spilling off the penny" and who can place the most drops of alcohol on the penny without spilling off the penny." Name of team member Number of drops of water on penny Number of alcohol drops on penny 1. What property of water is being evaluated with this experiment? Why did you get the results that you observed? Part C. Pepper Shake some pepper on top of water in a small dish that is provided. Using the toothpicks that I provide, touch first one end of the toothpick and then the other in the water. One appears darker in color so that you will be able to record your results. What happens to the water and pepper when each end is touched? 1. What do you think - is pepper polar? Why do you think this? 2. What do you think about the material on the opposite end of the toothpick - is it polar? Why do you think this? Part D. Wax Paper Place a small drop of water on a piece of wax paper. Describe its shape. Try cutting it in half with a toothpick that does not have two different colors.

5 What happens to the drop? s 1. What property of water is being evaluated with this experiment? 2. Would it matter if you place the droplet of water on loose leaf paper as opposed to wax paper? Why or why not? Part E. Needle Place some water in an evaporating dish and float a needle on top of the water. Describe the difficulty or ease in doing this. 1. What property of water is being evaluated with this experiment? Is this a difficult task? Part F. Soda Bottle Eruption Demonstration Outside, we will use a 2 liter bottle of Diet Coke and a roll of Mentos to see how tall of an eruption we can make. First we will open the bottle of soda, then we will load the Mentos into a test tube to make it easier to load them all into the bottle at the same time. The big question is why do we see what we see. This bottle is not water, but carbonated - the fizz is stored under pressure, this is why you get that sound when you open the can or bottle. The carbon dioxide is suspended in the soda. The water molecules still exhibit surface tension - you think about it and research it and see who can answer the question - WHY? ( write your response here)