Freezing and Melting of Water - Experiment | CH 100, Lab Reports of Chemistry

Download Freezing and Melting of Water - Experiment | CH 100 and more Lab Reports Chemistry in PDF only on Docsity! CH 100: Fundamentals for Chemistry Lab 1 Instructor: Tony Zable Freezing and Melting of Water Freezing temperature, the temperature at which a substance turns from liquid to solid, and melting temperature, the temperature at which a substance turns from a solid to a liquid, are characteristic physical properties. In this experiment, the cooling and warming behavior of a familiar substance, water, will be investigated. By examining graphs of the data, the freezing and melting temperatures of water will be determined and compared. Figure 1 MATERIALS IBM-compatible computer 400-mL beaker LabPRO water Logger Pro 10-mL graduated cylinder Vernier Temperature Probe ice ring stand salt utility clamp stirring rod test tube PROCEDURE Part I: Freezing 1. Put about 100 mL of water and 5 to 6 ice cubes into a 400-mL beaker. 2. 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 water bath. Place a temperature probe into the water inside the test tube. 3. Prepare the computer for data collection by opening “Exp 02” from the Chemistry with Computers experiment files of Logger Pro. The vertical axis will have temperature scaled from –20 to 30°C. The horizontal axis will have time scaled from 0 to 15 minutes. 4. When everything is ready, click Collect to begin data collection. Then lower the test tube into the ice-water bath. Experiment: Freezing & Melting of Water CH 100: Fundamentals for Chemistry Lab 2 Instructor: Tony Zable 5. Soon after lowering the test tube, add 5 spoons of salt to the beaker and stir with a stirring rod. Continue to stir the ice-water bath during Part I. Important: Stir enough to dissolve the salt. 6. 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 ice cubes to the beaker as the original ice cubes get smaller. 7. When 15 minutes have passed, data collection will stop. Keep the test tube submerged in the ice-water bath until Step 10. 8. 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. Press the mouse button and hold it down as you drag across the flat part to select it. • 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 9. Prepare the computer for data collection. From the Data menu, choose Store Latest Run. This stores the data so it can be used later. To hide the curve of your first data run, click the Temperature vertical-axis label of the graph, and uncheck the Run 1 box. Click OK . 10. Click Collect to begin data collection. Then raise the test tube and fasten it in a position above the ice-water bath. Do not move the temperature probe during Part II. 11. Dispose of the ice water as directed by your teacher. Obtain 250 mL of warm tap water in the beaker. When 12 minutes have passed, lower the test tube and its contents into this warm-water bath. 12. When 15 minutes have passed, data collection will stop. 13. On the 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. Experiment: Freezing & Melting of Water