Name: _____________________
Testing for simple sugars and starch activity
Carbohydrates are an important organic compound found in all living things. The main function
of carbohydrates is to produce energy that is needed for organisms to carry out life processes
(MRSGREN).
The two major forms of carbohydrates are:
● Simple sugars, such as fructose (fruit sugar), glucose, and lactose (milk sugar),
which are found in fruits, honey, sugar, and milk.
● Starches which are found in starchy vegetables, grains, rice, breads and cereals.
Benedict’s solution is an indicator that is used to test for the presence of most simple sugars (it
cannot test for sucrose, table sugar). When a simple sugar (like glucose or fructose) is present,
Benedict's solution will change color from blue to green to orange. The more sugar there is, the
more drastic the color change will be. Heat is required for the indicator to work.
Iodine solution is an indicator that is used to test for the presence of starch. When starch is present,
Iodine solution will change color from dark orange (amber) to a blue/black .
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Procedure 1:
Purpose: To investigate the presence of starch in 3 solutions
Materials:
1 test tube containing water
1 test tube containing glucose solution
1 test tube containing starch solution
Iodine solution (starch indicator)
Method:
1. Add 10 drops of iodine solution to each test tube.
2. Carefully swirl the test tubes to mix the contents.
3. Observe any color changes.
4. Record your observations in table 1 (page 3).
Procedure 2:
Purpose: To investigate the presence of simple sugars in 3 solutions
Materials:
1 test tube containing water
2 test tubes containing glucose solution
1 test tube containing starch solution
Benedict’s solution (simple sugar indicator)
Hot water bath
Method:
1. Add 10 drops of benedict’s solution to each test tube.
2. Place all test tubes except 1 of the test tubes containing glucose into the hot water bath, heat for 2
minutes.
3. Observe any color changes.
4. Record your observations in table 1 (page 3).
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Table 1: Colors observed in each test tube
Material tested
Indicator solution used
Water
Starch
Glucose
Glucose (no heat)
Iodine solution
Benedict’s solution
Questions:
1. What is the main function of carbohydrates? _________________________
__________________________________________________________
2. What are 2 major forms of carbohydrates? __________________________
3. Carbohydrates are organic compounds, what 2 types of atoms must they
contain? ________________________________
4. Benedict’s solution tests for the presence of: ________________________
5. Iodine solution tests for the presence of: ___________________________
6. Which indicator requires heat to work? ____________________________
7. Which indicator shows a + result when it turns orange? _________________
8. Which indicator turns blue/black when it has a + result? ________________
9. How did your results from procedure 2 prove that heat is needed for Benedict’s
solution to react with glucose? ___________________________________
__________________________________________________________
10.
How did your results from procedure 2 prove that just heating Benedict’s
solution is not enough for it to change color but that glucose must also be
present? ___________________________________________________
__________________________________________________________
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