Test how oxygen affects the amount of vitamin C contained in orange juice
Suitable For
Grade 8
Difficulty
3
Time Required
<2 Weeks
Supervision
Required
What’s it about?
‘Vitamin C’, also known as ascorbic acid, is one of the essential vitamins for good health. The actual function of ‘Vitamin C’ is to maintain strong connective tissue. If a person has an inadequate amount over a long period of time, they will suffer the deficiency disease called ‘scurvy’. We all know how important it is to get enough ‘Vitamin C’ in one’s diet, but how long does Vitamin C in fruit juice last? Find out in the following science experiment:
Topics covered
Vitamin C, Indicator, Iodine
What will I need?
- ORANGE JUICE
- MEDICINE DROPPER
- TAP WATER
- BOWL
- CORNSTARCH
- IODINE SOLUTION
- 6x PLASTIC CUPS
Procedure (Method)
‘Vitamin C’, also known as ascorbic acid, is one of the essential vitamins for good health. The actual function of ‘Vitamin C’ is to maintain strong connective tissue. If a person has an inadequate amount over a long period of time, they will suffer the deficiency disease called ‘scurvy’. We all know how important it is to get enough ‘Vitamin C’ in one’s diet, but how long does Vitamin C in fruit juice last? Find out in the following science experiment:
- Use a mixing bowl to mix together one cup of water and about 2 table spoons of corn starch. Use a spoon to mix the corn starch well so that it completely dissolves in the water.
- Add iodine solution to the mixture in the bowl, one drop at a time, until the mixture in the bowl turns a dark purple-blue colour. This will be your ‘indicator’ solution.
- Place two table spoons (about 30ml) of the corn starch / iodine mixture into a plastic cup.
- To test the amount of Vitamin C contained in fresh orange juice, use a medicine dropper to soak up some fresh orange juice, and then one drop at a time, add the juice to the corn starch / iodine mixture in the plastic cup. Gently swirl the liquid in the glass after every few drops, while counting and recording how many drops of juice it takes to clear the purple-blue colour. This measures the concentration of vitamin C in the juice. Record the number of drops on a data table.
- Now, label 6 plastic cups with a magic marker, half of them ‘covered’ and the other half ‘uncovered’ and add exactly the same amount of orange juice into each of them. Cover only the ‘covered’ labelled cups with plastic wrap and place them all in the refrigerator.
- Using the same testing procedure as before (steps 3 & 4), test each of the orange juice samples after 24 hours in the fridge. Record the number of drops you used for each sample of juice in your data table.
- Re-cover the ‘covered’ cups and place them back into the refrigerator for testing again after another 24 hours.
- Repeat this procedure once every 24 hours for all the orange juice samples, until no more vitamin C is contained in it. The iodine / starch mixture will stay blue, no matter how much orange juice drops are added. Make sure you record your data after each testing session and draw up a chart & line graph comparing how long it took to eliminate the vitamin C from each sample type.
How does it work?
In this science experiment we use a ‘chemical reaction’ that changes the colour of an ‘indicator’ (iodine) when there is a certain concentration of ‘Vitamin C’ in a given volume of juice. When iodine is mixed with cornstarch and water, a deep purple-blue coloured substance is formed. When the juice drops are added and when enough Vitamin C is added to this ‘indicator’, the purple-blue colour disappears. The lower the amount of orange juice drops that is required to turn the purple-blue colour white, the more Vitamin C is contained in the given fruit juice!
Vitamin C is water-soluble, meaning it will dissolve in water. Vitamin C is sensitive to heat, light and exposure to air. Over time, the vitamin C in the orange juice will oxidize, meaning it will combine with the air. The uncovered cups will oxidize a lot quicker than the covered cups and will loose the vitamin C a lot faster!
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