Name__________________________
Lab Activity: Organic Compound (Carbohydrates) Testing Using
Chemical Indicators
Objective: By the end of this lab activity, you should be able to relate
specific compounds with their chemical indicators, and tell positive or
negative results for the three types of carbohydrates – monosaccharides
(simple sugars); disaccharides (complex sugars); and polysaccharides
(starches).
Directions: Each member of the lab group needs to record the results of
each chemical test in his lab notebook, and tell what each test tells him
about the presence or absence of the chemicals being tested. Make sure
you wear safety goggles for this lab activity.
Lab Instructions Part I: Testing Known Substances
In Part I, you will you will conduct chemical tests on known substances and
water. Part I will serve as a control.
Note: 1.0 mL = 20 drops from a pipet or dropper. All substances are in
solutions.
A. Chemical Test for Polysaccharide (Starch)
a. Number test tubes #1-4
b. To each test tube, add the following:
1.
2.
3.
4.
1.0 mL monosaccharide (simple sugar)
1.0 mL disaccharide (complex sugar)
1.0 mL polysaccharide (starch
1.0 mL water
c. Record the color of each solution before adding any
chemical indicator.
d. Add 5 drops of iodine solution to each test tube.
e. Record the color of each test tube.
B. Chemical Test for Monosaccharide
a. Number test tubes #1-4
b. To each test tube, add the following:
1.
2.
3.
4.
1.0 mL monosaccharide (simple sugar)
1.0 mL disaccharide (complex sugar)
1.0 mL polysaccharide (starch
1.0 mL water
c. Add 1.0 mL of Benedict’s solution to each test tube.
d. Record the color of each test tube.
e. Place the test tubes in a hot water bath. This is a
beaker filled with hot water. For this chemical test,
this will speed up any reactions. Be careful not to over
heat as this may give a false positive.
f. Record the colors of each test tube after heating.
C. Indicator Paper for Monosaccharide
a. Number test tubes #1-4 or you may use a spot plate.
b. To each test tube or well, add the following:
1.
2.
3.
4.
1.0 mL monosaccharide (simple sugar)
1.0 mL disaccharide (complex sugar)
1.0 mL polysaccharide (starch
1.0 mL water
c. Record the color of each solution before adding any
chemical indicator.
d. Dip a strip of Tes Tape into each test tube or spot
plate.
e. Record the color of the Tes Tape.
Lab Instructions Part II: Testing Unknown Substances
In Part II, you will conduct chemical tests on various sugars and starches
and determine whether each is a monosaccharide (simple sugar),
disaccharide (complex sugar), or polysaccharide (starch).
You will conduct test A (iodine solution), test B (Benedict’s solution), and
test C (Tes Tape) on the following substances. All of the substances are
types of carbohydrates.
Amylose
Glucose
Fructose
Sucrose
Lactose
D. Chemical Test for Polysaccharide (Starch) Using Iodine Solution
a. Number test tubes #1-7
b. To each test tube, add the following:
1.
2.
3.
4.
5.
6.
1.0 mL amylose
1.0 mL glucose
1.0 mL fructose
1.0 mL sucrose
1.0 mL lactose
1.0 mL polysaccharide (starch)
c. Record the color of each solution before adding any
chemical indicator.
d. Add 5 drops of iodine solution to each test tube.
e. Record the color of each test tube.
E. Chemical Test for Monosaccharide (Simple Sugar) Using Benedict’s
Solution
a. Number test tubes #1-8
b. To each test tube, add the following:
1.
2.
3.
4.
5.
6.
7.
1.0 mL amylose
1.0 mL glucose
1.0 mL fructose
1.0 mL sucrose
1.0 mL lactose
1.0 mL monosaccharide (simple sugar)
1.0 mL disaccharide (complex sugar)
c. Add 1.0 mL of Benedict’s solution to each test tube.
d. Record the color of each test tube.
e. Place the test tubes in a hot water bath. This is a
beaker filled with hot water. For this chemical test,
this will speed up any reactions. Be careful not to over
heat as this may give a false positive.
f. Record the colors of each test tube after heating.
F. Indicator Paper for Monosaccharide (Simple Sugar) Using Tes Tape
a. Number test tubes #1-8 or you may use a spot plate.
b. To each test tube or well, add the following:
1.
2.
3.
4.
5.
6.
7.
1.0 mL amylose
1.0 mL glucose
1.0 mL fructose
1.0 mL sucrose
1.0 mL lactose
1.0 mL monosaccharide (simple sugar)
1.0 mL disaccharide (complex sugar)
c. Record the color of each solution before adding any
chemical indicator.
d. Dip a strip of Tes Tape into each test tube or spot
plate.
e. Record the color of the Tes Tape.
Questions:
1. If you were testing an unknown solution for starch, how would you
know if starch is present or not?
2. What is the reason for test tubes #7 & #8 in Part II?
3. When you conduct a chemical test using Benedict’s solution, why do
you need to apply heat?
4. How could you determine if an unknown substance were a disaccharide
(complex sugar) from noticing the results of both monosaccharide
(Benedict’s & TesTape) tests?
5. Which of the unknown substances are polysaccharides (starches)?
6. Which of the unknown substances are monosaccharides (simple
sugars)?
7. Which of the unknown substances are disaccharides (complex sugars)?