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- In this lab, we will look at the intermolecular forces in the substance to predict which substance has the highest vapor pressure (thereby determining which has the greater boiling point).
Procedures
At your desk, determine the molecular polarity of xylene, (C8H8), methanol ( C1H3OH) and water.
In the lab
- Get a test tube rack and three large test tubes.
- Get three balloons (do not do anything with balloons especially blow them up)
- Get a 250ml beaker and fill it with approximately 150ml of tap water.
- Turn on heating element and place 250ml beaker on heater.
- In one large test tube, add approximately 2ml (w/pipette) of xylene, and then place balloon over top of test tube making sure to take all air out of balloon.
- In the another large test tube, add approximately 2ml (w/pipette) of methanol and then place balloon over top of test tube making sure to take all air out of balloon.
- Then in the final large test tube, add approximately 2ml (w/pipette) of water and then place balloon over top of test tube making sure to take all air out of balloon.
- Make observation of the condition of the balloon.
- Let heating element (hot plate) heat up the water bath & both of the test tubes (once boiling starts shut off heating element). Periodically, make observations on the condition of the balloons.
- When done heating system, remove the 250ml beaker with test tubes from the heating element (either by using a glove or let beaker cool down enough to touch) and let it cool on the table top.
- Observe the condition of the balloons after the water has cooled back down to room temperature.
Data Table
- Initial observation of balloons in water bath:
- Periodic observation of balloons:
- Final observation of balloon after cooling back to room temperature.
Questions
- Which substance has the higher vapor pressure and how did you know it?
- Did your results agree with what you predicted?