Vitamin C Experiment

Booperkit
Vitamin C: Which contains more, citrus fruits or green vegetables? 

(adapted from: https://www.unm.edu/~rbose/abose/science.htm)

Project Purpose

The purpose of this experiment is to detect and compare the concentration of vitamin C in several citrus fruit and green vegetable juices by titration of the juice with a corn starch-iodine vitamin C indicator solution.

Vitamin C:

One of the most important vitamins in our diet is vitamin C (which is also known as ascorbic acid), found in many fruits and vegetables. Vitamin C is also easily damaged or destroyed.

The best-known sources of vitamin C are the citrus fruits – oranges, lemons, limes, tangerines, and grapefruits. Good vegetable sources include peppers, tomatoes, parsley, dark leafy greens, and cabbage. Animal foods contain almost no vitamin C.

Vitamin C has many functions. It is needed for healthy bones, teeth, and gums; growth; strength of blood vessels; fast healing of wound; and increasing the body’s resistance to infection.

Hypothesis:

Some green vegetables contain more vitamin C than citrus fruits.

Experiment:

  • Test the concentration of vitamin C in a vitamin C tablet (the control sample) and in several citrus fruits and green vegetables.
  • To determine the concentration of a substance in a solution, chemists use the technique called titration. This means adding, in precise measured amounts, a reacting agent of known concentration until the solution changes color, indicating a chemical reaction.
  • Prepare a water solution of a vitamin C tablet, and juices of fruits and green vegetables.
  • The reacting agent in the experiment will be the corn starch-iodine vitamin C indicator solution.

Controlling Variables:

  1. The correct preparation of corn starch-iodine vitamin C indicator solution, and since this solution is unstable, it is freshly prepared each time it is used.
  2. The amount of corn starch-iodine vitamin C indicator solution used for each test sample should not vary during the experiment.
  3. Make a control sample of Vitamin C tablet solution to determine whether a weaker or stronger concentration of vitamin C is present in each fruit and vegetable juice tested.

Glossary of Terms:

Chemistry the study of matter.
Chemist one who studies the make ups and properties of substances and investigates how substances react with one another.
Chemical reaction a change that produces one or more new substances.
Comparing observing how things are alike or different.
Controlling variables identifying and managing factors that may influence the accuracy of an experiment.
Experiment testing under controlled conditions.
Hypothesis tentatively accepting an explanation as the basis for further investigation.
Inferring implying a conclusion from available evidence.
Interpreting data finding patterns or relationships in a set of data.
Titration adding, in precise measured amounts, a reacting agent of known concentration until the solution changes color (in our experiment, from royal blue to clear), indicating a chemical reaction.
Vitamins organic substances for the regulation of the metabolism and normal growth and functioning of the body.

Materials:

  1. 10 clear plastic or glass cups
  2. 10 plastic stirrers
  3. 1 dropper
  4. food processor
  5. large wire strainer
  6. hot plate
  7. cooking pot
  8. one 250 ml measuring cup
  9. two small bowls
  10. one gallon of distilled water
  11. starch-iodine vitamin C indicator
  12. two teaspoons of corn starch
  13. tincture of iodine
  14. Juices (some prepared and some ready made) of several citrus fruits and green vegetables
  15. one 100 mg vitamin C tablet

Process

  1. Prepare the juices that are not ready made and store them in the refrigerator in cups.
  2. Prepare a vitamin C standard. Place a 100 mg vitamin C tablet in a small plastic bag and crush it with a hammer into a powder. Add the powdered vitamin C into 100 ml of distilled water and mix them well. Pour into a closed container and store in the refrigerator.
  3. Prepared the corn starch-iodine vitamin C indicator solution.
    • Pour half a teaspoon of corn starch into the cooking pot.
    • Pour a cup of distilled water into the pot.
    • Heat and stir the pot of water and corn starch solution until all the cornstarch is dissolved in the water.
    • After heating, Let everything cool.
    • Pour two teaspoons of the solution and one cup of distilled water into one of the cups.
    • Using the medicine dropper, add four drops of tincture of iodine into the solution.
    • The color of the resulting solution should be royal blue.
    • At this point, the corn starch-iodine test solution is done.
  4. Titration of the vitamin C standard and the fruit and vegetable juices one at a time.
    • The procedure for the titration is carried out using the following steps.
      1. Place 25 ml of the corn starch-iodine indicator solution into a clear plastic cup.
      2. Use the medicine dropper to drop in the vitamin C standard or the juice of fruit or vegetable being tested.
      3. After each drop, stir the resulting solution.
      4. When the royal blue indicator changeS to clear, Stop adding the juice.
      5. Record the number of drops needed to change the royal blue indicator to clear.
      6. Repeat steps 1-5 above for each item being tested.

Results:

Show the results in a table and/or chart/graph.