Activity 5: Chemical Components of Some Foods

Concept: Simple Method of Determining Chemical Components of Food

Objectives:

1. Determine the chemical contents of some types of foods derived from plants and animals; and
2. Refer how these chemical components of food serve as the chemical basis of life.

Materials:

            Several pieces of waxed paper plate                   Tincture of iodine

            Brown blotting paper or bakery paper                 Benedict’s solution

Alcohol lamp                                                     Test tube holder

Newspaper                                                       Medicine dropper

10-12 test tubes (depends on the number of food samples to be tested)

Foods to be tested (ham, hotdog, corn, potato, flour, bread, celery stalk, sugar, candy, etc.)

Note: Formulate a problem and a hypothesis on the basis of chemical components of living things (based on the situation below) before starting with the tests. Write your hypothesis on the table provided.

Divide each food sample into three portions for the three types of test to be done:

Testing for the Presence of Starch

Procedure:

1. Spread the newspaper to cover the table or the work area.
2. Place small pieces of foods to be tested in the waxed paper plate.
3. Test each food sample for the presence of starch by putting three to five drops of iodine solution.
4. Observe the food samples if there is a change in color after putting iodine solution.
5. Write your observations and results.

Testing for the Presence of Sugar

Procedure:

1. Cut the food samples into small pieces and put enough amounts in each test tube.
2. Pour Benedict’s solution in the food sample.
3. Light the alcohol lamp and heat the test tubes with food samples. (Use test tube holders)
4. Observe the changes in color of the food samples.
5. Write your observations and results.

Testing for the Presence of Fats

Procedure:

1. Spread the brown blotting paper.
2. Put the food sample in it.
3. Observe the brown paper on the basis of the amount of fats it absorbed when the sample were place in it.
4. Write your observations and results.

Name: ____________________________________ Date: _______________

Subject: ___________________________________ Rating: _____________

Activity 5 Action Sheet: Chemical Components of Some Foods

Concept: Simple Method of Determining Chemical Components of Food

Problem: Test for the Presence of Starch

Hypothesis:

            Hypothesize whether the food samples contain starch, sugar or fats or not. Write a positive sign (+) or a negative sign (-) to indicate its presence or non-presence. Use the same symbols for the tested hypothesis.

Observations:

Conclusions: