Title Melting and Freezing Point Curves Lab標(biāo)題的熔化和凝固點(diǎn)曲線的實(shí)驗(yàn)室

1、.Chemist: _Period: _ Date:_Melting and Freezing Point Curves LabPurpose: Introduction: If you have ever cooled a glass of water with ice cubes and watched water vapor condense on the outside of a glass, you know water can exist in distinct physical states: the solid state (ice), the liquid state (wa

2、ter), and the gaseous state (water vapor or steam). In any pure substance, changes of physical state occur at constant, discrete temperatures that are uniquely characteristic of the substance. Changes in physical state include solids melting, liquids freezing or boiling, and gases condensing. For ex

3、ample, water freezes at 0C and ice melts at 0C. During the freezing/melting phase change, the temperature of the mixture of ice and water stays 0C until all of the ice melts OR all of the water freezes. Liquid water boils at 100C and water vapor condenses at 100C. During the boiling/condensing phase

4、 change, the temperature stays at 100C until all of the water vaporizes OR all of the water condenses.In this experiment, you will closely examine what happens when a pure substance undergoes a change in physical state. You will examine the freezing and melting behavior of an organic compound called

5、 tert-butyl alcohol. During this experiment, you will be concerned with two questions: 1) does tert-butyl alcohol begin to freeze at the same temperature that solid tert-butyl alcohol begins to melt? And 2) What happens to the temperature of tert-butyl alcohol between the time that melting or freezi

6、ng begins and the time that freezing or melting is completed? You will also consider what happens to the energy that is put into or removed from the tert-butyl alcohol system during melting and freezing.Materials: Tert-butyl AlcoholThermometerCopper WireRing StandTwo 400ml BeakersLarge Test TubeRubb

7、er StopperWire RingUtility ClampBunsen BurnerStrikerBackground: 1. If a substance is melting is the substance absorbing heat or releasing heat?2. If a substance is freezing is the substance absorbing heat or releasing heat?3. Describe TWO ways we can determine the change in heat in a given substance

8、.Procedure:Most of the equipment is already set-up for you.1. Each test tube contains 10ml of tert-butyl alcohol, a thermometer, and a copper wire. Please Do NOT Remove them from the Test Tube.2. Obtain two 400ml beakers. Fill one beaker with 200ml of ice cold water, and the other beaker with tap wa

9、ter.Part A1. Use a utility clamp to support the test tube and its contents in the Room temperature tap water beaker. Make sure that the portion of the test tube that contains the tert-butyl alcohol is immersed in the water. The test tube is NOT to touch the bottom of the beaker. The thermometer is N

10、OT to touch the bottom of the test tube, but should be immersed in the tert-butyl alcohol.2. Use a Busen burner with a very low flame and gently heat the water in the beaker. 3. Use the copper wire to stir the tert-butyl alcohol by moving it up and down in the solution. While carefully but continuou

11、sly attempting to stir the alcohol, read and record the temperature of the tert-butyl alcohol every thirty seconds. Continue recording the temperature until the temperature reaches 35C.Part B1. Carefully replace the beaker containing hot water (Be Very CAREFUL) with the beaker containing the ice col

12、d water. Make sure the portion of the test tube containing the tert-butyl alcohol is immersed in the the water. The test tube is NOT to touch the bottom of the beaker. The thermometer is NOT to touch the bottom of the test tube, but should be immersed in the tert-butyl alcohol.2. Use the copper wire

13、 to stir the solution by moving it up and down in the tert-butyl alcohol. Use the copper wire to stir the tert-butyl alcohol by moving it up and down in the solution while recording the temperature on your data table every thirty seconds.3. Continue recording the temperature until all of the tert-bu

14、tyl alcohol is solidified 20C. (Note: When most of the tert-butyl alcohol is solidified, you will no longer be able to stir the contents of the test tube. Continue taking readings during this period.)Data Table:*If you need more time add rows to the end*Cooling TimeTemperatureHeating TimeTemperature

15、30sec30sec60sec60sec90sec90sec120sec120sec150sec150secAnalysis:1. Construct a graph of your data from Part A. Plot the temperature verses time. Choose a scale that fills the entire page of the paper. Be sure to label your x and y-axis as well as give the graph a title. Draw a smooth curve through th

16、e points and label the line appropriately as the Melting Point Line.2. Plot the data from Part B on the same graph and draw a smooth curve appropriately label the line as the Freezing Point Line.Conclusion:1. Does the temperature of a substance change while melting or freezing? Explain.2. Using the

17、data from Part A, determine the melting point of tert-butyl alcohol.3. Using the data from Part B, determine the freezing point of tert-butyl alcohol.4. Does the tert-butyl alcohol melt and freeze at the same temperature? Explain.5. Explain the shape of the curves in terms of the energy changes that are occurring at the molecular level as the sample heats up to melt, and as it cools down to freeze.6. You have used 10ml of tert-butyl alcohol in this experiment. Explain how an increase in the amount of tert-butyl alcohol used would affect the shape of the curves and the melting