Intermolecular Forces Lab


(No formal lab report required.� Just complete this sheet and follow its instructions.)


Purpose:� The purpose of this lab is to determine the relative strength of the intermolecular forces between water, ethyl alcohol, and acetone.




  1. Find a thermometer that has no gaps in the liquid inside the thermometer.� If your thermometer contains mercury, be especially careful not to break the thermometer.
  2. Tear a C-Fold paper towel in half.� Tear each of the resulting pieces in half.� Tear those four pieces in half.
  3. Tightly wrap one of the eight pieces of paper towel around the end of the thermometer containing the liquid reservoir.� Use masking tape to securely and tightly hold the paper towel piece in place, keeping the masking tape as far away from the liquid reservoir as possible.
  4. Dip the thermometer bulb into a test tube of water that is at room temperature.� Take care not to get any water on the masking tape.� Record the temperature reading on the thermometer before you remove it from the liquid.� Always be as precise in your temperature readings as possible.� (Remember this hint on all future labs involving thermometers.)
  5. Start your stopwatch as you remove the thermometer from the liquid and immediately position the bulb of the thermometer in front of a fan that is set to its highest speed possible.� Try to position the bulb where the airspeed is highest.
  6. Record the lowest temperature that is reached and record the time required to achieve that temperature.
  7. Remove the masking tape and paper towel.� Wipe the thermometer dry and allow it to return to room temperature.
  8. Repeat steps 3-7 for ethanol, by dipping your thermometer into the small Erlenmeyer flask filled with ethanol.
  9. Repeat steps 3-7 for acetone, by dipping your thermometer into the small Erlenmeyer flask filled with acetonel.




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Questions (Answer on a separate piece of paper and staple it to this sheet):


  1. Draw a Maxwell-Boltzman distribution for these specific experiments, and use your diagram to explain why the temperature dropped in the above experiments.
  2. Draw a separate Maxwell-Boltzman distribution that you can use to answer each of the following questions:� Which of the three liquids has the lowest intermolecular forces based on your data?�Which has the highest?� Explain your answers based on the intermolecular forces and/or molecular geometry of each molecule.
  3. Using a different Maxwell-Boltzman distribution than those you drew for questions 1 & 2, explain why one of the liquids had a greater temperature drop than the others?
  4. Which of the three liquids should have the lowest b.p.?� Which should have the highest?