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The Effect of Temperature on the Vitamin C Content of Lemon Juice

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Introduction

Biology IA The Effect of Temperature on the Vitamin C Content of Lemon Juice 2013 Design Aim To investigate the effect of changing temperature on the Vitamin C content of lemon juice Research Question How does changing temperature the temperature of lemon juice effect its Vitamin C content? Variables Independent Variable – Temperature of Lemon Juice (°C) Dependant Variable Vitamin C content as measured by the number of drops taken to turn the DCPIP solution colourless Results Raw Data Table showing the effect of changing temperature on the Vitamin C content of lemon juice shown by the number of drops of lemon juice required to turn DCPIP colourless. Temperature of the lemon juice (°C) ±1 Number of drops of lemon juice required to turn DCPIP colourless Observations Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 20 3 3 2 3 3 The juice quickly went pink then colourless. 30 8 8 7 7 6 The juice quickly went pink then colourless. 40 10 10 10 9 9 The lemon juice went pink then colourless. 50 14 13 12 12 11 The juice slowly went pink then colourless. 60 20 18 16 10 16 The juice slowly went pink then colourless. Processed Data Table showing the effect of changing temperature on the Vitamin C content of lemon juice shown by the number of drops of lemon juice required to turn DCPIP colourless Temperature of the lemon juice (°C) ...read more.

Middle

This result would have greatly lowered my mean, if I ignore the value from the fourth trial the mean for 60°C increases to 17.5 instead of 16 so my results are not as accurate. The consistency of my other results means I can assume that this outlier was due to systematic errors. My results are reflected by these other experiments such as the one a found online which directly measured the concentration of vitamin C in different fruit juices at varying temperatures. Their results are shown in the table below. The findings were very similar to my own, as the temperature increases the vitamin C content also decreases. “It can be seen from analytical results that the lower the temperature the better the concentration of Vitamin C in fruit juice.”³ Therefore I can conclude that my findings and my explanation is correct as it is confirmed by an outside source. Evaluation: Limitation of the method How significantly could this have impacted on your results and why Improvement When we diluted our lemon juice we didn’t use distilled water we used tap water. The distillation process removes many of the impurities present in regular tap water or drinking water. These impurities in the water could have interfered with the experiment. As tap water contains other chemicals, compounds and minerals which have the potential to also reduce or prevent the reduction of the DCPIP solution. This would have effected both the reliability and validity of my results. ...read more.

Conclusion

While conducting the experiment our lemon juice samples were left exposed to air. When oxygen in the air reacts with vitamin C, oxidation occurs which is a chemical change that results in the breakdown of this vitamin.â´ This would have caused some of our lemon juice samples to have a decreased vitamin c content due to the prolonged oxygen exposure, this would have caused more drops to be added to cause the solution to decolourise due to the combined breaking down of vitamin c from oxygen and temperature. We could cover the test tubes containing our 1ml samples and our beaker with the diluted lemon juice with clingfilm to reduce the exposure to air. While conducting the experiment our lemon juice samples were left exposed to natural and artificial light. Photodegradaton occurs when vitamin C is exposed to natural and artificial light. â´ This would have caused some of our lemon juice samples to have a decreased vitamin c content due to the prolonged light exposure, this would have caused more drops to be added to cause the solution to decolourise due to the combined breaking down of vitamin c from light and temperature. In a future experiment we could conduct it in a cupboard to completely reduce light exposure or we could conduct it in a totally artificially lit room to ensure that the exposure to light remained consistent throughout the experiment. Sources 1) http://uk.answers.yahoo.com/question/index?qid=20110221071452AA0OHqv 2) http://www.ask.com/question/how-does-temperature-breakdown-ascorbic-acid 3) http://www.pjbs.org/pjnonline/fin1877.pdf 4) http://www.enotes.com/homework-help/how-does-exposure-air-light-temperature-affect-310886 ...read more.

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