Distillation
A basic laboratory process in organic and agricultural chemistry is distillation. Based on the glass vessels and tubes shown in the picture (below), Carver had a laboratory with such a capability. Carver found that by heating and then collecting evaporated liquids from different mixtures he could find different applications for agricultural products.
Distillation Explorations
In this part students take a fruit, make a solution or mash, add yeast and sugar to the solution, allow it to ferment for a day, then distill the liquid to separate the alcohols and esters that may be hidden in the mixture. This can be done as a student laboratory, a demonstration, or hybrid where students do part of the exploration by extracting sugars and various organic solutions from fruits and vegetables, and a central distillation station is used to determine their products.
Carver often said, "There is no short cut to achievement. Life requires thorough preparation -- veneer isn't worth anything." This exploration requires some careful preparation and operation. It will be the persistent student and teacher who finds interesting results in this experience.
Getting Started--The Mash
Students will first prepare a mash from ingredients they choose, old bananas, other fruit, sugar and yeast. This mash will be prepared ahead of time so that it can ferment and be ready for distillation.
Materials Needed
• Overripe fruits (The produce person at the grocer may be able to help here or students can bring in things they find at home that may be outdated.)
• Plastic containers
• A masher, blender or shredder to reduce fruit to pulp.
• Sugar (if sugar is to be leached from beets, then see Extracting Sugar)
• Yeast
Procedure
1) Place mashed fruit in a container with equal portions of warm (not hot) water. Add 1/4 teaspoon of yeast and 1 cube or 1 teaspoon of sugar to the mix.
2) Allow the mixture to ferment in a warm place overnight
3) The "mash" will be ready the next day.
Distillation
An apparatus that will work nicely for this exploration is detailed in the following video. For background information about distillation see: Distillation Theory
Materials Needed
• Sturdy glass vessel such as an Erlenmeyer flask or narrow-mouthed glass jar.
• Cork or stopper with a hole for tubing. The stopper must fit the mouth of the jar.
• Aluminum foil
• Paper towel
• Hot plate
• Shallow pan
• Piece of plastic tubing with copper wire or copper tubing
• Tape
• Small cup
Procedure
1) Set up the apparatus as shown in the video. For a step-by-step procedure, see Step-by-step procedure
2) Pour the liquid of the mash into the vessel to be heated. This should be liquid only and contain no pieces of solid matter. Make sure that the amount of liquid in the container is small--no more that 100 ml or so as it will take too long to heat and cool if a large volume is used.
3) Apply heat slowly. If using a non-pyrex vessel, the hot plate should be warmed only until boiling of the alcohols starts. Since the temperature of the liquid is not being monitored in this apparatus, caution should be used to keep the hot plate at medium heat.
4) Watch the boiling carefully and observe any leaks of steam in the system. If there are, note the problem and cool the apparatus to make adjustments and try again. Do not attempt to fix the hot apparatus.
5) The gas generated by the bubbling mash will travel through the aluminum tube and cool as it comes near the cooled sides of the metal. Soon a drip should start at the end with the cup. The distillate can be saved in the cup.
6) Observe smell and test for alcohol with a sobriety detector, if available. In the example below, the smell was powerfully fruity and the meter showed .10 when placed at the top of the vial--over the legal limit!
STEM Challenge: Going Deeper
Review with students the process of distillation and the utility of extracting alcohols, esters and other organic compounds. Certain kinds of oils, spices, and chemicals are not soluble in water and can only be extracted with alcohol.
Ethanol has many uses such as a fuel source, as a solvent for industrial applications, as a solvent for certain spices such as vanilla, as a solution for certain drugs, and as a solvent for certain plant compounds.
Ethanol is also the primary alcohol found in alcoholic beverages. The amount of alcohol distilled will be very small in this experiment. Even so, strict controls should be observed by the teacher. It should also be reminded here that nothing in these experiments should be tasted or eaten. Consider all experiment materials as non-edibles.
Students can use their apparatus and process to extract interesting compounds created by the fermentation process. To explore these options click here: Other Distillation Compounds
Assessment
The standards for this exploration may be found at NGSS:
PS1.A: Structure and Properties of Matter
• Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it. (MS-PS1-3)
• In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. (MS-PS1-4)
•The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.(MS-PS1-4)
Process: Students should keep track of their observations and data in their STEM Notebook. Assessment of recording of the experimental materials, data and outcomes can be conducted by examining the notebook and comparing it to an assessment rubric such as this example.
Content: An objective assessment can be given to assess students understanding of the distillation cycle. A diagram of the basic components of the boiling/evaporation of a liquid, the vaporization of the gas, and the condensation of a liquid can be stylized and then vocabulary (see below) or concepts affixed to each phase. See an example here.
Vocabulary: Distillation, Distillate, Evaporation,Condensation,Condenser, Boiling Point, Fermentation, Alcohol, Ester