Orange ripening and vitamin C
The materials required for the science fair project:
- 1 ripe orange
- 1 half ripe orange
- 1 unripe orange
- 3 beakers
- 1 juice extractor
- 1 burette
- 1 bottle of iodine - starch solution
- 1 glass stirring rod
- 1 stand and holder to support the burette
- 1 measuring cylinder
1. For this science fair project, the independent variable is the type of orange used – ripe, half ripe and unripe. The dependent variable is the number of iodine-starch drops required to neutralize the vitamin C in the juice, determined by dropping iodine-starch into the orange juice until the solution turns blue. The constants (control variables) are the amount of orange juice, the concentration of iodine and the temperature of the environment, which will remain at room temperature.
2. Label the 3 beakers as ripe, half ripe and unripe respectively. Use the juice extractor to extract the juice from each orange. Measure 100ml of each type of orange juice with the measuring cylinder, and pour into the appropriate beaker.
3. Mount the burette on the stand and pour the iodine-starch solution into the burette.
4. Place the beaker of ripe orange juice under the burette. Add the iodine-starch solution to the orange juice one drop at a time, by adjusting the burette. After each drop, the blue iodine-starch will react with the vitamin C and become clear. Once all the vitamin C has neutralized, the color of the iodine-starch will not clear, but instead remain blue. Stop the procedure and record the number of drops taken to neutralize the vitamin C in a table, as shown below.
5. Repeat step 4 with juice from the half ripe and unripe oranges.