The Bonding Lab

Purpose:

  1. Using 7 unknown liquids, create a standard

graph of evaporation rates using a temperature probe.

  1. Identify these 7 unknown liquids on a boiling

point graph, given the structural formulas for

known solvents.

Materials:

7 Unknown liquids, filter paper, rubber band, computer, Labpro device, temperature probe.

Equipment:

Lab Pros, computers, direct connect temperature probes.

Procedure:

  1. Print the graph labeled “Standard Boiling Point Graph”, which contains the 14 solvents, and the sheets that contain the structures of the 14 solvents. These will be in the folder marked “Evaporation Lab-Student” on the desktop.
  2. Print off the actual structures of the solvents, labeled “Solvents 1” and “Solvents 2”. These can be found in the same folder. You will need two copies of each page.
  3. Cut out the solvents, and attempt to identify which ones have strong physical bonding, and which ones have weak physical bonding. This will require you to place two of the same molecule close to one another, in order to identify the physical bonding present.
  4. Order these 14 solvents in order of boiling point, from lowest to highest, based on the strength of the physical bonding.
  5. Of these 14 solvents, 7 will be given to you for identification.
  6. Wrap filter paper around the end of a temperature probe and secure with a rubber band.
  7. Run the file marked “Evaporation Lab” in the “Evaporation Lab” on the desktop. You will collect data for unknown solvents A through G. Make sure to start all liquids close to the same initial temperature!
  8. Be sure that you tighten the lid on each liquid sample immediately after using!
  9. Be sure to analyze all seven samples.
  10. Save your standard graph of evaporation ratesand print for analysis.

Conclusion:

  1. You will first want to identify the 14 solvents on the boiling point graph. Make sure you label each of the 14 solvents on the boiling point graph, using your above analysis of physical bonding.
  2. As discussed above, of the 14 solvents on the sheet, only 7 were given to you for analysis and identification. Using both graphs and analysis, identify and LABEL each of the seven liquids on your standard graph of evaporation rates you created.
  3. Discuss, if relevant, any relationships witnessed during the experiment between these two graphs and physical properties of substances! For example, what physical properties can be observed about a substance with a high boiling point? A low boiling point?
  4. IMPORTANT - Explain, in detail, why the differences in evaporation rate occur (why you chose the boiling points you did for each liquid). A discussion of structures and physical bonding present for each molecule is required! You should go through each of the 7 molecules, and discuss them individually, as well as do a comparison discussion!