The Phase Change Lab: Freezing and Melting of Water Experiment 3 Freezing temperature is the temperature at which a substance turns from a liquid to a solid. Melting temperature is the temperature at which a substance turns from a solid to a liquid. Freezing temperature and melting temperature are characteristic properties. In this experiment, you will determine and compare the freezing and melting temperatures of water. OBJECTIVES In this experiment, you will use a computer to measure temperature analyze graphs of your data to determine the freezing and melting temperatures of water determine the relationship between the freezing and melting temperatures of water analyze a graph of temperature versus time for a substance undergoing a change of temperature and a change of phase. apply the concepts studied in a new situation MATERIALS computer Go!Link adapter Logger Pro software Vernier Temperature Probe ring stand utility clamp one test tube 400-mL beaker water 10-mL graduated cylinder ice salt spoon Figure 1 Physical Science with Computers 3-1
Experiment 3 PROCEDURE Part I Freezing 1. Turn on your computer. Select Physics to login. 2. Connect the temperature probe to a Go!Link adapter. Connect the Go!Link/tempererature probe set-up to the computer s USB port. 3. Open LoggerPro by selecting the LoggerPro icon from the dock (it has a red diamond background with a caliper in front of it). 4. Go to the File menu and select open. Prepare the computer for data collection by opening the file named 03 Freeze Melt Water.cmbl (it is located in the folder Physical Science with Computers). When the file opens, the vertical axis will have temperature scaled from 20 to 30 C. The horizontal axis will have time scaled from 0 to 15 minutes. 5. Put about 100 ml of snow (or crushed ice) into a 400-mL beaker. 6. To the snow, add 5 spoons of salt to the beaker and stir with a spoon. All of the salt should dissolve; you may need to add more salt. 7. Put 5 ml of water into a test tube and use a utility clamp to fasten the test tube to a ring stand. The test tube should be clamped above the snow bath. Place the Temperature Probe into the water inside the test tube. 8. When everything is ready, click the Collect button to begin data collection. Then lower the test tube into the snow bath. 9. Throughout the entire 15 minutes, make and record observations. A data table is provided. 10. Slightly, but continuously, move the probe during the first 10 minutes of Part I. Be careful to keep the probe in, and not above, the ice as it forms. When 10 minutes have gone by, stop moving the probe and allow it to freeze into the ice. Add more snow & salt to the snow bath as the original snow melts. 11. When 15 minutes have passed, data collection will stop. Keep the test tube submerged in the snow bath until Step 13. 12. On the displayed graph, analyze the flat part of the curve to determine the freezing temperature of water: Move the mouse pointer to the beginning of the graph s flat part (plateau). Press the mouse button and hold it down as you drag across the flat part to select it (only select the flat part). Click on the Statistics button,. The mean temperature value for the selected data is listed in the statistics box on the graph. Record this value as the freezing temperature in your data table. To remove the statistics box, click on the upper-right corner of the box. Part II Melting 13. Prepare the computer for data collection. From the Experiment menu, choose Store Latest Run. This stores the data so it can be used later. 14. Click the Collect button to begin data collection. Then raise the test tube and fasten it in a 3-2 Physical Science with Computers
Freezing and Melting of Water position above the snow bath. Do not move the Temperature Probe during Part II. 15. Throughout the entire 15 minutes, make and record observations. A data table is provided. 16. Obtain 250 ml of warm water in a clean beaker. When 12 minutes have passed, lower the test tube and its contents into this warm-water bath. 17. When 15 minutes have passed, data collection will stop. 18. On the newer displayed graph, analyze the flat part of the curve to determine the melting temperature of water: Move the mouse pointer to the beginning of the graph s flat part. Press the mouse button and hold it down as you drag across the flat part to select it. Click the Statistics button,. The mean temperature value for the selected data is listed in the statistics box on the graph. Record this value as the melting temperature in your data table. To remove the statistics box, click on the upper-right corner of the box. 19. Print a graph of temperature vs. time showing both data runs: Label both curves by choosing Text Annotation from the Insert menu, and typing Freezing Curve (or Melting Curve ) in the edit box. Then drag each box to a position on or near its respective curve. double-click on the title of the graph. Add the initials of each member of your lab group to the title of the graph. Go to the File menu and select Print Graph. Print copies of the graph for each member of your group. 20. Clean-up your lab station and return all equipment. Dispose of the salty ice water as directed by your teacher. Physical Science with Computers 3-3
Experiment 3 DATA Freezing temperature of water sample C Melting temperature of water sample C OBSERVATIONS TIME TEMPERATURE PHASES OF MATTER OBSERVATIONS PART #1 0 MIN 2 MIN 4 MIN 6 MIN 8 MIN 10 MIN 12 MIN 14 MIN 15 MIN PART #2 0 MIN 2 MIN 4 MIN 6 MIN 8 MIN 10 MIN 12 MIN 14 MIN 15 MIN PROCESSING THE DATA: ANSWER ALL QUESTIONS USING 3-4 Physical Science with Computers
COMPLETE SENTENCES. 1. What happened to the water temperature before the water started freezing? Freezing and Melting of Water 2. What happened to the water temperature during freezing? 3. What happened to the water temperature after all of the water was frozen? 4. What happened to the water temperature before the water started melting? 5. What happened to the water temperature during melting? 6. What happened to the water temperature after all of the ice was melted? 7. According to your data and graph, what is the freezing temperature of water? Physical Science with Computers 3-5
Experiment 3 8. According to your data and graph, what is the melting temperature of water? 9. How does the freezing temperature of water compare to its melting temperature? 10. How many phases of matter are present at the freezing temperature of water? What are they? 11. How many phases of matter are present at the melting temperature of water? What are they? ERROR 1. Calculate the percent error between your value for the freezing temperature of water and the accepted value for the freezing temperature of water. SHOW YOUR WORK. % error =[(theoretical-experimental)/theoretical] x 100 2. Calculate the percent error between your value for the melting temperature of water and the accepted value for the melting temperature of water. SHOW YOUR WORK. % error =[(theoretical-experimental)/theoretical] x 100 3. List (using complete sentences) at least three sources of error that may have affected your freezing temperature or your melting temperature. 3-6 Physical Science with Computers
Freezing and Melting of Water APPLICATION 1. Phenyl salicylate has a freezing temperature of 41.5 C. On the graph below, sketch and label a freezing curve for phenyl salicylate. Be sure to indicate the freezing temperature on the graph. 2. Using another color, draw a melting curve for phenyl salicylate on the same graph. Indicate the melting temperature on the curve. Temperature versus Time Graphs for Phenyl Salicylate Temperature ( C) Time (minutes) CONCLUSION: ON A SEPARATE SHEET OF PAPER, NEATLY HANDWRITE OR TYPE A THOROUGH CONCLUSION TO THIS LAB. Restate the objectives in your own words. Summarize the procedure in three to four sentences. Describe your graphs in detail. What happens to the temperature of water before, during, and after a phase change? Restate your freezing temperature data and your melting temperature data. Make an analysis of what your data means. How does your data relate to the objectives? Compare your data with the accepted values of 0 C. How good is your data? Identify at least three sources of error and how each would affect your results. State a one-sentence conclusion. Physical Science with Computers 3-7
Experiment 3 Name: Block: Date: / / The Phase Change Lab & Conclusion (2) On a separate sheet of paper, neatly handwrite or type a thorough conclusion to this lab. (2) Restate the objectives in your own words. (2) Summarize the procedure in three to four sentences. (4) Describe your graphs in detail. What happens to the temperature of water before, during, and after a phase change? (2) Restate your freezing temperature data and your melting temperature data. (3) Make an analysis of what your data means. How does your data relate to the objectives? Compare your data with the accepted values of 0 C. How good is your data? (3) Identify at least three sources of error and how each would affect your results. (2) State a one sentence conclusion. (4) Lab is complete with data and observations. (11) Lab processing questions are answered completely using sentences. (3) Error questions are complete and work is shown. (2) Application section of the lab is complete. TOTAL: /40 3-8 Physical Science with Computers