Name ______date ______

Laboratory Investigation

Testing for Organic Compounds

Purpose: To identify which organic compound is present in an unknown substance.

Hypothesis: ______

______

Materials: 5 test tubestest tube holderclamphot plate

goggles1 500 ml beakerwaterunknown substance

Indicators(reagent): Biuret’s (protein)Iodine (starch)

Benedict’s (glucose)Sudan (lipid)

Safety: Goggles will be worn AT ALL TIMES (even during your write-up). The indicators can irritate

the skin and eyes. Handle glassware carefully. Use caution when using the hotplate.

Notify the teacher immediately in the event of a cut, burn, break, or spill.

Procedure:

Assign 1 lab partner who will bring test tubes to supply station for each task. ______

Name

  1. Bring 1 test tube to supply station to obtain unknown sample. Fill almost to the top.
  2. At your lab table, divide the sample equally among 4 test tubes.

Carbohydrates / Proteins / Lipids
Iodine color / Starch Present / Benedict’s color / Sugar present / Biuret’s color / Protein present / Separation
present

Starch Test

  1. Add 2 drops of iodine indicator to test tube while the tube is in the test tube holder
  2. Swirl test tube a few times to evenly distribute the indicator.
  3. Place back into holder.
  4. Write your result in the table above.

Sugar Test

  1. Add 10 drops of Benedict’s solution to a second test tube.
  2. Swirl test tube a few times to evenly distribute the indicator.
  3. Carefully place test tube in hot water bath and boil for 5 minutes.
  4. Remove test tube with clamp and place in test tube holder.
  5. Look at chart below to determine results and record observations.

Benedict’s sugar indication colors

Blue(original color)negative – no sugar

Greenish bluetrace amount of sugar

Green+ small amount of sugar

Yellow++ medium amount of sugar

Orange+++ high amount of sugar

  1. Write your result in the table above.

Protein Test

  1. Add 6 drops of Biuret’s solution to a third test tube.
  2. Swirl test tube a few times to evenly distribute the indicator.
  3. Observe any color change.
  4. Write your result in the table above.

Lipid Test

  1. Add 4-5 drops of Sudan to fourth test tube.
  2. Swirl test tube a several minutes to evenly distribute the indicator.
  3. Write your result in the table above.

Analysis:

Conclusion (complete sentences): ______