Paula MoltzanLab partner: Sean SchaffersOctober 31, 2017TA: Bryan Novas (L-42)Chromatography, Evaporation, and Intermolecular Forces Introduction:The purpose of this lab was to measure and calculate the retention factor of known and unknown dyes as well as observe temperature changes caused by the evaporation of solvents, compare their rates of evaporation and then relate the temperature changes to the strength of intermolecular forces within the molecules. Matter exists in three states: solid, liquid, and gas. transition from one to another requires a transfer in energy. The molecules in the liquid state are in constant motion and are close enough that attractive forces between molecules influence their movements, which gives them their characteristic properties. Molecules are bound together by intermolecular forces each of which varies from molecule to molecule. These forces impact how strong the bond between atoms in the molecule are. When looking at the intermolecular forces inliquids, chromatography/ vaporization can show how strong or how weak the forces holding the molecule together are. In part A of this experiment we tested 7 known, 1 unknown, and 1 unknown food color dye solutions. Once a chromatography paper was obtained, a line was drawn1 cm from the bottom of it as well as sectioned evenly into 9 sections. Using glass capillary tubes, we placed a uniformed dot of each solution on the chromatography paper in its designated spot, cleaning the applicator thoroughly with distilled after each solution. Once all of the spots dried, we placed the paper (sample end down) into the chromatography chamber that has NaCl solution in it. Making sure not to let the paper touch the edge of the chamber or sit too deep in the solution at the bottom of the chamber. We let the paper develop for 25 min, removing the paper when the solvent was within 1.5 cm of the top. Once the paper dried, we measured and recorded the distance the solvent traveled and the distance the dye traveled. With this information, we calculated the RF value for each dye. This allowed us to compare the interactions the dye had with the solution and the paper. In part B, we placed a thermometer in a buret clamp and putting a tightly folded Kimwipe on the end of the thermometer, and secured it with a rubber band. Then we immerse the wrapped portion of the thermometer into a vial containing the solvent for one minute, remove the thermometer from the vail and cap it, then the initial temperature was recorded. Then every 20 seconds the temperature was recorded until it reached a minimum temperature or until 10 minutes has passed. Then we removed the Kimwipe and cleaned thermometer. We repeated the above steps for all 7 solvents, recording the data and any observations along the way. Evaporation rates were calculated with the observed data, dividing the change in temperature by the total time. Safety glasses must be worn at all times during the experiment, gloves are optional but the dyes we will be working with may stain your skin. Some of the solvents we will be using are flammable, treat the with respect and keep them away from open flame or other heat sources. Leftover dye solutions can be put down the drain because they are nonhazardous and water soluble. Dye papers, Kimwipes, rubber bands, and chromatography paper may be disposed of in a general lab trashcan, but the glass capillary tubes must be disposed of into the broken glass box. Any contaminated evaporation solvents must be disposed in the appropriately labeled hazardous waste container.Discussion: In part of this experiment, we measured and calculated the retention factor of known and unknown dyes and related the retention factors to the known molecular structures of each dye. Brilliant Blue FCF (B1) and Fast Green FCF (G3) had the most similar Rf values at 0.848 and 0.857 respectively. When comparing these two dyes Rf value to their molecular structure, it would make sense that they have the same interaction with the paper because they both have very similar molecular structures. Two other dyes that showed similar Rf values were Tartrazine (Y5) and Sunset yellow FCF (Y6), both of these dyes also have very similar molecular structureswhich would explain their Rf similarities. The dye with the lowest Rf value was Erythrosine(R3) which showed as the color pink. Erythrosine has the most compact molecular structure, meaning it should and did have the smallest interaction with the chromatography paper. When deciding which colors were in the unknown dye B, we easily able to see that R3 was present in the mixture because that color stopped moving 2.3 cm from the starting point, it was a little more difficult to examine the other colors present in the mixture. This is because I believe it was a mixof B1 and R40, the color expressed was purple and measured to be 6.1 cm from the start positionwhich is close to the average of the B2 and R40. With this information, it was decided that the unknown dye contained the colors Brilliant blue, Allura red, and Erythrosine. In part B of this experiment, observed temperature changes cause by evaporation of different liquids and compared their rates of evaporation. We then related the temperature changes to the strength of intermolecular forces within these molecules. Out of the seven liquids that we used in this experiment, Methanol had the highest evaporations rate of 15C/min and water had the slowest evaporation rate of 0.59C/min. In the case of water this make sense that it has the slowest evaporation rate because water is a polar molecule which has hydrogen bonds, which are the strongest bond and the most difficult bonds to break apart. In the case of methanol,it does not make sense that it would have the fastest evaporation rates because it is also a polar molecule and has hydrogen bonds, so I would have guess that it would have a similar evaporation rate water. I would have guessed that n-pentane would have the fastest evaporation rate because it is a non-polar molecule with London dispersion forces, which are the weakest intermolecular forces. Liquids with London dispersion bonds like n-pentane, hexane, and heptane should have faster evaporation rates than polar molecules with dipole-dipole and hydrogen bonds because bond between London dispersion can easily be broken down to their gaseous state. The test liquids were divided into four groups, group A liquids were polar liquids, group B were non-polar liquids. In