FSC 12
Where's the Fat?
Introduction:
The science of separating substances is essential in the production of materials. Although impurities may
not be a problem in some cases, they lower the quality of the final product and can make foods,
beverages, and medicines dangerous to consume. Separation science also increases production efficiency
by enabling manufacturers to separate and reuse materials important to producing finished goods.
Separation and reuse of component materials can also reduce waste and help conserve landfill space.
In this laboratory exercise, students examine a process used to separate substances—extraction.
Fat is soluble in nonpolar solvents, such as acetone, and may be extracted from snack food by crushing
the food and mixing it with the solvent. The solvent, which may contain suspended solid particles, is
transferred by pipet to another container. The solid is allowed to settle to the bottom, and the supernatant
liquid (liquid above a precipitate) is removed by decanting (pouring). The solvent (acetone) is evaporated,
the extracted fat that is left behind is weighed. The efficiency of the separation is determined.
Purposes:To learn extraction procedures by separating fat from a snack food.
To analyze the effectiveness of chemical extraction procedure by comparing actual lab results with
predicted results based on the snack food's label information.
Materials:
acetone
snack food (thin foods that allow complete penetration of the solvent, such as potato chips and corn puffs,
work best)
Apparatus:
watch glasses / petri dishes (MUST BE GLASS!!)
2 test tubes
beakers
mortar and pestle
plastic transfer pipets
rubber stoppers
Laboratory safety
Acetone is volatile, so be sure to keep it away from fire or sparks.
Procedure:
** Record observations of materials for each step of the procedure. **
Name of snack food: ________________________
1. Mass a sample of snack food (0.45—0.50 g) and crush it using a mortar and pestle. Mass the crushed
food. Transfer the crushed food to a test tube.
2. Add acetone (3 mL) to the test tube.
3. Stopper the test tube and shake for several seconds.
4. Remove the stopper and pipet the liquid into the second test tube, using the plastic micropipet. Do not
allow any solid to be transferred to the second test tube.
5. Add another portion of acetone (3 mL) to the first tube. Stopper the test tube and shake. Pipet the liquid
into the second test tube – try to transfer as much liquid as possible.
6. Allow the liquid in the second test tube to sit for 2 to 3 min.
While you are waiting, mass a watch glass or petri dish.
7. Decant (pour) the supernatant liquid in the second test tube onto the watch glass. Fill a beaker with hot
tap water and place the watch glass on the beaker in the fume hood to evaporate the solvent overnight.
8. Wipe the condensation off the bottom of the watch glass and mass the watch glass and the extracted fat.
Experimental data - Make a data table that incorporates the data and observations that you obtained as
well as the calculations that you do regarding the data.
Name of snack food: ________________________
1. Mass of crushed snack food: ________
2. Mass of watch glass: _______
3. Mass of watch glass and extracted fat: _______
4. Mass of extracted fat: _______
5. Observed percent of fat in snack food: ______
(mass of extracted fat/mass of crushed snack food) X 100%
6. Theoretical percent of fat in snack food derived from label information: _______
(mass of fat per serving/mass of serving size) X 100%
7. Percent error of extraction:________
[(experimental data–label info) / label info] x 100
Analysis:
1. Was all the fat in the snack food extracted? If not, why? How could the experiment be changed to
recover more fat?
2. Why was only the fat extracted from the snack food?
3. Why were the extracts of acetone combined in the second test tube?
4. How would the separation efficiency change if you changed the volume of solvent from 3 mL to 0.3
mL? Why?
5. How would the separation efficiency change if you crushed the snack food into very fine particles
instead of large pieces? Why?
6. Compare your results to others in the class. Create a continuum with your experimental data of amount
of fat % (least to greatest).
7. What types of snack foods were more accurately assessed? (i.e. were closer in value to the label info).
8. Based on the phase state of the fat (solid or liquid), what type of fat did you extract? (saturated or
unsaturated).
9. Examine the ingredient list of the snack food. What ingredients would be considered fats?
10. From the ingredient list, were any of the fats hydrogenated? What does this term mean and how is it
related to whether the fat was liquid or solid in the Petri dish?
11. Examine the ingredient list and using the “Comparing Fats” sheet (given to you in class), do the fat
ingredients correspond to what would be on the list? (i.e., if there was coconut oil in the food, you’d
expect there to be saturated fats – and thus more solid in nature.
** This lab is adapted from the Carolina AP Science Curriculum
Typical data:
Corn chips
Popcorn
Potato chips
Corn puffs
65 %
85 %
90 %
95 %