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Measuring Vitamin C content in different substances

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BIOLOGY Analysing the Vitamin C content in fruit juices - experiment write-up Aim: I'm going to investigate the concentration of Vitamin C (ascorbic acid; C6H8O6) in various fruit juices and to compare them. This experiment will see the following fruit juices going under experimentation: pineapple, orange and papaya juice. I'm going to use these juices because I expect these to have large amounts of vitamin C and this should allow me to get good results. Hypothesis: I predict that the orange juice will have the highest Vitamin C concentration. From my own knowledge, a citrus fruit such as the orange is rich in ascorbic acid, more commonly known as Vitamin C. Much is not known about the pineapple or the papaya, therefore I can safely assume that the orange juice will have the highest concentration of vitamin C in it out of the 3 fruit juices. Apparatus: * Standard 1% Vitamin C solution (Acts as the control) * Pineapple Juice (From a fresh, brand new carton) * Orange Juice (From a fresh, brand new carton) * Papaya Juice (From a fresh, brand new carton) * 1% DCPIP (Dichlorophenol-indophenol) solution (Turns colourless when in the presence of Vitamin C) Standard lab glassware/equipment: > Measuring cylinder (To measure out accurately the volumes of fruit juice), > Pipettes (Used to extract the juices from carton with contaminating ...read more.


After the orange juice came the pineapple juice in 9.48 seconds and lastly, papaya juice in 10.23 seconds. Conclusion: In conclusion, my hypothesis was proven correct. The orange juice did have the highest concentration of Vitamin C out of the three fruit juices we experimented with. This is because oranges are naturally rich in Vitamin C. However, I cannot say that the experiment was entirely reliable; therefore the results could prove to be invalid. Evaluation: Our experiment went well, and our hypothesis was proven successful, however I feel that the method could have been improved to get more accurate results. In Step 1, I felt that using a higher volume of Vitamin C solution would be better; there would be more moles of ascorbic acid. This would get a better control value, especially if a larger volume is used. I don't feel that the other juices will comply and correlate with this control, if a small volume of Vitamin C is used. Therefore, increase the volume of the control, and the fruit juices, especially if the DCPIP happens to be in excess. Furthermore, more DCPIP will mean that the accuracy of the results will be improved, and they will correlate as the amount of DCPIP increases with the amount of fruit juice used. ...read more.


There is a big difference in variation with subspecies of fruit, age and season of fruit. We also had to make sure that the fruit juices were not heated any point, because heating Vitamin C causes it to be destroyed. Also, during our experiment, we used our pipettes from a storage box. Some of the other groups working on the same experiment were taking pipettes from there as well. Therefore, there is a chance that the same pipette was used to pipette up two or more of the fruit juices. This means that the samples used were contaminated, and our results could be invalid and effectively unreliable. There is also a chance that heating the fruit juice will concentrate the Vitamin C, therefore the decolourisation would be inaccurately quick. The results, in the end, would not support the hypothesis. There is also a reason to believe that the fruit juice companies add extra artificial ascorbic acid to increase its concentration. Moreover, if the squeezed fruit juice is left out exposed to the air, there could be a considerable difference in the concentration of Vitamin C. Lastly, due to the fact that other chemicals like sodium sulphite can react with DCPIP, if they are present in the juice, then it will be unfair to accept the results, unless we assume that the only reducing agent is Vitamin C. ?? ?? ?? ?? Biology ...read more.

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Response to the question

Adequate essay. Response to the question overall is average for this level and presents the information in a adequate way to a high standard exploring different methods of presenting the data. One or two things could be improved such as ...

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Response to the question

Adequate essay. Response to the question overall is average for this level and presents the information in a adequate way to a high standard exploring different methods of presenting the data. One or two things could be improved such as the scientific research behind the data and types of tests used.

Level of analysis

Aim is not very well researched, and should actually research the different already published values of different values in the different fruits to make an educated opinion on which fruits to use, rather than assuming they have quite a lot of vitamin C in them. The candidate admits to little knowledge about two of the fruits so I am not sure they were a safe comparison in this instance. Does not investigate if the amount of fruits contained in the fruit juice are consistent throughout so not to bias the amount of vitamin C found in them. Includes chemical equations and pictures which boosts up the level of the candidates work. Graph used to compare results is quite hard to understand and not appropriate to show the results from the experiment. Could do more statistical tests to prove or reject the hypothesis such as the chi squared test. Considers a range of different improvements and things that may have gone wrong with the experiment but could have expanded by calculating possible percentage errors of the different equipment.

Quality of writing

Dialect and level of words used are not to a very high scientific standard. Grammar is okay but stumbles in some places. Punctuation and spelling are fine.

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