Phase Changes of t-Butyl Alcohol

Introduction In this experiment you will discover what happens to the temperature of a substance during a phase change (solid to liquid or liquid to gas) and in between phase changes. You will monitor the temperature of the substance as you add and remove heat from the system.

Materials 1 large test tube t-butyl alcohol hot plate ring stand with utility clamp 2 400-mL beakers temperature probe ice LoggerPro computer program

Procedure 1. Half fill a large test tube with t-butyl alcohol and insert the temperature probe into the liquid. 2. Set up a 400-mL beaker three-fourths full of water and place the test tube in the bath. Heat the water up quickly. Continually stir the alcohol while heating to avoid splattering. The liquid, t-butyl alcohol, will begin to boil inside the test tube before the water in the beaker boils. While one partner is stirring the alcohol, have the other partner go on to the next step. 3. Make sure that the temperature probe is connected to Port 1 on the Serial Box. 4. Launch “Logger Pro.” Open the “Chemistry with Computers” folder, then “Exp 04.” Make sure that the y-axis of the graph is labeled “Temperature” with a scale from 0-100oC and that the x-axis of the graph is labeled “Time” with a scale from 0-10 minutes. 5. If the t-butyl alcohol is in a rolling boil, you may go on to the next step. 6. Click the COLLECT button. It will take a few seconds for graphing to begin. Be careful not to click STOP until you are finished with the experiment. 7. While the temperature is being monitored by the computer, go get some ice with a little water in a 400-mL beaker. If the temperature of the boiling liquid has been monitored on the graph for at least one minute, go on to the next step. 8. While keeping the temperature probe in the alcohol, remove the test tube from the hot water. Carefully place it into the ice-water bath and turn off the hot plate. Stir the t-butyl alcohol while it is cooling by moving the temperature probe up and down through the alcohol. Be careful not to pull the probe out of the liquid. Monitor the temperature until the t-butyl alcohol has frozen completely and the temperature has stabilized for at least one minute. Click the STOP button. 9. Select the STATISTICS button and read the maximum and minimum temperatures in the box. Record the these temperatures in your lab notebook as the boiling point and freezing point of t-butyl alcohol. 10. Title your graph “Cooling Curve for t-Butyl Alcohol.” Print the graph. Enter your group name and the number of copies you need for each group member. 11. Lift the test tube out of the ice water. Place it back in the warm water bath to melt. Clean up your lab station.

Phase Changes of t-Butyl Alcohol CHEM Analysis 1. Neatly attach your graph in your lab notebook. Indicate (with a highlighter) and label the regions of your graph that correspond to the following processes: a) boiling b) freezing c) cooling a liquid

2. Label the following temperatures on the y-axis: a) freezing point b) boiling point

Conclusions For each of the three regions you labeled in analysis #1, describe the following:  the temperature of the alcohol,  the kinetic and potential energy of the alcohol molecules, and  the behavior of the alcohol molecules.

Phase Changes of t-Butyl Alcohol CHEM