Evaporation Lab

Evaporation Lab

Armed with but a couple of temperature probes and some suspicious clear carbon compounds we ventured into the world of the unknown.  We took two probes and wrapped the ends in filter paper to soak up the chemicals we were testing.  We tested two substances at a time and dipped them in first the methanol and ethanol, then the propanol and butanol, and finally the hexane and heptane.  We taped the two probes over the edge of the counter so they could evaporate freely and without interference.  Once they were completely evaporated we recorded the readings.  After the initial readings of the methanol and ethanol and based on the number of carbons we guessed that the temperatures of the next four would be higher because of the greater number of carbons.  We were fairly right to assume this.

 This pre-lab chart shows the formulas of the substances we used and is what we based our estimations on.  Because we were able to count how many carbons were in each substance we were able to determine whether the temperature went up or down with the number of carbons and whether or not the presence of a hydrogen bond had any effect on the temperatures.

This is the table of our actual and predicted measurements of the probes.  As you can see our guesses were pretty close because we had already determined that the temperature rose from methanol to ethanol.  The last two are much more off because we hadn't determined quite what sort of effect the hydrogen bond had.  Apparently, the lack of a hydrogen bond sort of starts the pattern over.

In this image the green line represents the methanol and the red line represents the ethanol.  According to this, the more carbons present in the compound, the quicker the temperature change is.

In this image Propanol is the red line and butanol is the green one.  While they're pretty close the higher carbon wins out again and creates the most dramatic change.

Here, hextane is the red line and heptane is the green line.  Once again the greater carbon had a more dramatic change. Don't be alarmed by the rise in the temperature of the probe with the heptane.  It just took hextane a lot longer to level out than heptane.  We believe this was simply because they aren't as close together as the previous ones were carbon-wise as our teacher was out of the substance we were originally supposed to use.

Whoops, I misread my own tables the first time I wrote this conclusion.  I'll try again.  As my table at the top shows, the shift in temperature becomes smaller as the amount of carbons in the molecular sequences increases.  However, when there is no hydrogen bond as with heptane and hextane, the temperature shift grows with the amount of carbons.  But, fewer carbons tends to mean a greater shift in temperature from the beginning to completion of evaporation.