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Lab Report
Title:
Testing for the presences of sugars, non-reducing sugars, proteins, and starch
Statement:
Through a series of different solutions, different reagents will be added to determine the solution
type. Each of the unnamed solutions will be one of the following: a sugar, non-reducing sugar,
protein or starch. For every solution, there will be a reagent that will force a change. No two
solutions will ever react in the same manner. To test for sugars, Benedict’s reagent would cause a
change to the color orange/red-brown. To test non-reducing sugars, hydrochloric acid and
Sodium hydrogen carbonate will be added for color change to yellow, orange, and red tones. To
test proteins, biuret reagent would be added in order for a color change to purple. To test starch,
iodine solution would be added to test for a color change to blue-black.
Hypothesis:
If I test the four unnamed solutions with the correct reagents, then I will find a sugar, nonreducing sugar, protein and starch.
When benedict’s solution is added, the one solution that turns to red-brown is the solution with
sugar present.
When hydrochloric acid, sodium hydrogen carbonate, and benedict’s solution is added, the one
solution that turns red ( that did not turn red in the experiment dealing with sugars) is the solution
with non-reducing sugar present.
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When biuret’s reagent is added, the one solution that turns purple is the solution with protein
present.
When iodine solution is added, the one solution that turns dark blue/black is the solution with
starch present.
Materials:

Sugar solution

Non-reducing sugar solution-

Protein solution

Starch solution

Benedict’s reagent

Biuret Reagent

Iodine solution

Hydrochloric acid

Sodium hydrogen carbonate

4 small beakers (50 mL)

1 big beaker (200mL)

4 pipets

4 test tubes

Test tube rack

Test tube clamp
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
Hot plate

Sink

Labels

Paper towel

Paper

Writing utensil
Procedure:
First I put on my goggles, and then I gathered all the materials I needed. These materials
included getting all the reagents, 10 mL of the solutions into a small beaker, a hot plate, test
tubes, test tube holders, and test tube rack. Then I began to set up my work area. I number
labeled each beaker with solutions in them. Then I measured out 2 mL of each solution and
poured them individually into 4 test tubes, and I labeled each test tube with their respective
solutions. For each test tube I dropped in 2 drops of Biuret’s reagent to test for proteins. After
watching the solution turn into a different color, I noted down which solution changed into the
correct color. I picked up all the test tubes and went to wash them out. After I washed them I
dried them and I began to test more solutions. I measured out 2 mL of each solution again and
poured them into separate test tubes. Then I added 2 drops of Iodine solution to each test tube
and watched for a color change. After a change, I noted the solution that changed and went to
clean the test tubes out. Then I plugged in the hot plate to test for the sugar and non-reducing
sugars. I got the larger beaker (200mL) and filled it up with 100mL of water then I placed the
beaker onto the hot plate and waited for the water to come to a boil. As I was waiting I out 2 mL
of each unknown solution into the test tubes again. Then I put 2 dropped of Benedict’s reagent
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into each test tube, once the water came to a boil, I put the test tubes into the water and watched
for a color change. Once a few minutes passed by, I recorded the color changes, took out the test
tubes and cleaned those out. Then I filled each test tube with 2 mL of each unknown solution.
Then I added 2 drops of Hydrochloric acid into the test tubes, and then I put the test tubes back
into the heated water. Once the test tubes were heated for a while, I took the tubes out and added
Sodium hydrogen carbonate. After that I added more benedict’s reagent and placed the tubes
back into the heated water. I waited a few minutes and noted any color changes. Then I
unplugged the hot plate. I took out all the test tubes and went to wash them out. After the hot
plate cooled down I took the beaker off to clean that and put away the hot plate. I put away all
materials and wiped down my work space.
Testing for sugars1.
Put on your goggles; make sure they are on the whole experiment.
2.
Gather all materials: the reagents (Benedict’s reagent), 10 mL of the unknown
solutions into a small beaker, pipets, a hot plate, a larger beaker filled with 100 mL of
water, test tubes, test tube holders, and test tube rack.
3.
Place the four test tubes on the test tube rack.
4.
Label these test tubes (numbering the test tubes with their corresponding
unknown solution).
5.
Plug in the hot plate and place the beaker with 100mL on top, wait for this to
come to a boil.
6.
Using pipets obtain 2mL of each unknown solution and place each separately into
the 4 test tubes.
7.
Waiting for the water to boil, add 2 drops of benedict’s reagent into each test tube.
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8.
Once the water boils, place the test tubes into the heated water.
9.
Turn down the power keep the water boiling, but not overflowing.
10.
Wait a few minutes for a color change.
11.
Record all color changes and the solution that turns to orange and red brown is the
one with sugar present.
12.
Unplug the hot plate and take out all four test tubes using a test tube holder and
place them back on the rack.
13.
Wait for the solutions to cool, then take the test tube to the sink and wash out the
solutions.
14.
Clean the test tubes and let them dry.
Testing for non-reducing sugars1.
Put on your goggles; make sure they are on the whole experiment.
2.
Gather all materials, the reagents (benedict’s reagent, hyrodlic chloric acid, and
sodium hydrogen carbonate) 10 mL of the unknown solutions into a small beaker, pipets,
a hot plate, a larger beaker filled with 100 mL of water, test tubes, test tube holders, and
test tube rack.
3.
Place the four test tubes on the test tube rack.
4.
Label these test tubes (numbering the test tubes with their corresponding
unknown solution).
5.
Plug in the hot plate and place the beaker with 100mL on top, wait for this to
come to a boil.
6.
Using pipets obtain 2mL of each unknown solution and place each separately into
the 4 test tubes.
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7.
Waiting for the water to boil, add 2 drops hydrochloric acid to each test tube.
8.
Once the water boils, place the test tubes into the heated water.
9.
Turn down the power keep the water boiling, but not overflowing.
10.
After a couple minutes take the test tubes out using the test tube holder and place
the tubes back on the rack.
11.
Now add the sodium hydrogen carbonate, wait a minute, then add 2 drops of
benedict’s reagents.
12.
Place the test tubes back into the heated water.
13.
Wait a few minutes for a color change, and then note all observations.
14.
The solution that turns yellow, orange, or red is the one that has a non-reducing
sugar present. However this solution must have changed colors in only this experiment,
not in the first experiment testing for sugars.
15.
Unplug the hot plate and take out all four test tubes using a test tube holder and
place them back on the rack.
16.
Wait for the solutions to cool, then take the test tube to the sink and wash out the
solutions.
17.
Clean the test tubes and let them dry.
18.
Put away all materials and clean work area.
Testing for proteins1.
Put on your goggles; make sure they are on the whole experiment.
2.
Gather all materials, the reagents (biuret’s reagent) 10 mL of the unknown
solutions into a small beaker, pipets, test tubes, and test tube rack.
3.
Place the four test tubes on the test tube rack.
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4.
Label these test tubes (numbering the test tubes with their corresponding
unknown solution).
5.
Using pipets obtain 2mL of each unknown solution and place each separately into
the 4 test tubes.
6.
Add 2mL of biuret’s reagent into each test tube.
7.
Wait a few minutes to observe a color change.
8.
Note any observations.
9.
The solution that turns to purple is the solution with proteins present.
10.
Clean and wash out the test tubes and let them dry.
Testing for starch1.
Put on your goggles; make sure they are on the whole experiment.
2.
Gather all materials, the reagents (iodine solution) 10 mL of the unknown
solutions into a small beaker, pipets, test tubes, and test tube rack.
3.
Place the four test tubes on the test tube rack.
4.
Label these test tubes (numbering the test tubes with their corresponding
unknown solution).
5.
Using pipets obtain 2mL of each unknown solution and place each separately into
the 4 test tubes.
6.
Add 2mL of iodine solution into each test tube.
7.
Wait a few minutes to observe a color change.
8.
Note any observations.
9.
The solution that turns dark blue, almost black is the solution with starch present.
10.
Clean and wash out the test tubes and let them dry.
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11.
Put away all materials and cleanup work area.
Results:
Testing for sugar, solution 1 turned a peach color, solution 2 turned clearish tan with blue on the
bottom, solution 3 turned dark orange with brown on the bottom, and solution 4 turned yellow
green. Therefore sugar was present in solution 3.
Testing for non-reducing sugar, solution 1 turned dark yellow/orange red, solution 2 remained
clear, solution 3 became dark red brown, and solution 4 turned clear blue. Therefore nonreducing sugar was present in solution 1.
Testing for starch, solution 1 turned yellowish, solution 2 turned deep blue/ black, solution 3
remained clear with some yellow on top, and solution 4 also turned yellowish as solution 1.
Therefore solution 2 had starch.
Testing for proteins, solution 1 remained clear, solution 2 turned blue, solution 3 remained clear
with a slight hint of blue, and solution 4 turned purple. Therefore solution 4 contained proteins.
Testing for sugar
colors:
Solution 1
Solution 2
Solution 3
Solution 4
Peach
Clear tan, blue
Dark orange,
Yellow green
bottom
brown bottom
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Testing for non-
Dark yellow,
reducing sugar
orange red
Clear
Dark red brown
Clear blue
Deep blue/black
Clear, yellow on
Yellow
colors:
Testing for starch
Yellow
colors:
Testing for
top
Clear
Blue
protein colors:
Clear with slight
Purple
tint of blue
See Appendix A for pictures of each of the test.
Conclusion:
Each solution had a clear change in color and every test worked out as planned. Each solution
was able to be identified as a sugar, non-reducing sugar, protein, and starch. Therefore my
hypothesis that each solution will be able to be identified will be accepted. From the data, it was
clear that solution 1 is a non-reducing sugar, solution 2 is a starch, solution 3 is a sugar, and
solution 4 is a protein. When the Benedict’s reagent was added to the solutions, solution 3
changed to a yellow red color with brown on the bottom. Therefore my hypothesis will be
accepted due to the fact that solution 3 was the only solution that turned to the correct color.
When the hydrochloric acid, sodium hydrogen carbonate, and benedict’s solution was added,
solution 1 turned dark yellow, orange-red, and it did not turn this color during the experiment for
sugar, therefore my hypothesis will be accepted. When biuret’s reagent was added, solution 4
was the only solution that turned purple therefore my hypothesis will be accepted. When iodine
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solution was added, solution 2 was the only solution that changed to the deep blue/black color
therefore accepting my hypothesis. I learned that to properly test these experiments, there must
be patience and that time must be taken to pay attention to the little details. Similar to life, things
must be done with patience to get proper results. Possible sources of error include that the pipets
did not have the measurements labeled; therefore each test was an approximation. Another
possible source of error is that the paper labels fell into the heated water; this could have altered
some weird properties. There were also an inaccurate number of drops when adding the reagents,
using 2 drops for some test and 3 for others.
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Appendix A:
Testing for sugar
Testing for non-reducing sugar
Testing for Proteins
Testing for starch