chem 1 lab worksheet

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5 do 00 Intermolecular Forces Laboratory 12 ) 0 Laboratory ID No. Name Course/Section 12 Instructor Partner's Name (if applicable) Date (of Lab Meeting Worksheet PART I. EXPLORATION Data Collection 1. Roll a piece of paper towel into a small cylinder and wrap a rubber band around it to keep it from unraveling. Stick the end of the thermistor into the center of the roll and push in until the tip of the thermistor is just inside the other end of the roll. Set this assembly aside for a moment. 2. Start your Microlab interface and plug your thermistor into the Microlab. Create a new experiment that has Temperature on the y-axis and Time on the x-axis. 3. Pour ~1 mL of methanol into a small test tube. Place the test tube into your test tube holder and insert the thermistor with the roll into the test tube. 4. After the thermistor has sat in the liquid for about 1 minute, start recording data on your Microlab. After 30 seconds of taking data, remove the thermistor from the test tube and set it on the table top with the roll hanging off the edge of the table. 5. Once the temperature stops changing you can stop the Microlab experiment. Data Analysis 1. What happened to the temperature during the evaporation of the solvent? Is this process endothermic or exothermic? Sketch a picture of how you picture heat flow at the molecular level. 87 Expens PART II. POLAR COMPOUNDS Data Collection 1. Look at your data for the methanol run completed in Part I. What is the total temperature change, AT, for the evaporation of methanol? How long did it take? Fill out the table at the end of the section (some information you will need to look up online). 2. Using clean, dry test tubes for each run, repeat the data acquisition process from Part I using ethanol for one run and propanol for another. Fill out the data table with the data you take and information you look up. Data Analysis 1. What similarities and differences do you see between the compounds? Find three trends seen in the data. Explain the reasons for these trends. They all lose heat as they evaporate. but inside the fathe they buin heat 2. Find one of your trends that has a linear relationship and graph it. Using your graph, predict the same property for the next alcohol in the sequence, butanol. How close was your prediction? Look up that property for butanol and calculate a percent error. Sketch your graph below and show your work for your prediction. Intermolecular Forces Laboratory 12 PART III. NONPOLAR COMPOUNDS Data Collection 1. Based on the trends you saw for the polar compounds, predict the AT trend you will see for the nonpolar compounds pentane, hexane, and heptane. Explain your reason for choosing the order you did. 3 dishes es popn 2. Perform the same experiment as in Part II with the three nonpolar compounds, and fill out the data table. Does your data support your predicted trend from step 1? If not, what was different about the trend? Why do you think it was differ- Hane ent from what you predicted? Hexane Heptane it appears that the heat loss is slower comparts to the other polar compounds. Takes more time also. | Hexune lossess heat with time Data Analysis 1. What similarities and differences do you see between the compounds? Do you see the same three trends you saw with the polar compounds in Part II? Explain. N? 2. Try to find a different trend to form a linear graph than the trend used in Part II, and graph it. Predict the property value of the next alkane in the sequence, octane. How close was your prediction? Look up that property for octane and calculate a percent error. Sketch your graph below and show your work for your prediction. 89 Chemistry 141 Experimental Chemistry Data Table Compound Formula Structure AT (°C) Time to Evaporate (s) Methanol 23.3=20 llos Ethanol Propanol Pentane Hexane Heptane Compound Molar Mass ΔΗ Boiling Point (°C) vap Vapor Pressure @20 °C (approx.) Methanol Ethanol Propanol Pentane Hexane Heptane
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Explanation & Answer

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1. During the evaporation of the solvent, the temperature reduced. The aspect is due to the fact
that more energy was needed to break the bond between the liquid fir the vapor to be released.
The reaction is thus an endothermic reaction.
22.

2. All of them loss hest as they evaporate,as externally the temperature reduces . However, in the inside
they gain more heat energy that bre...


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