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To investigate how temperature affects the concentration of vitamin C in orange juice (specifically 'Just Juice').

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Biology Coursework -Vitamin C Apparatus: Burette, Test tubes, Retort stand, Bunsen burner, Measuring Cylinder, Beaker. Materials: Orange juice, Water, Indicator (Dichlorophenolindophenol) abbreviated (DCPIP) Burette filled with 50 cm3 DCPIP Orange juice Aim: To investigate how temperature affects the concentration of vitamin C in orange juice (specifically 'Just Juice'). Hypothesis: I predict that if I increase the temperature of the orange juice, the concentration of the orange juice will decrease. This is because vitamin C is a fairly unstable molecule, and the greater the heat the more vitamin C molecules will be broken down. It takes activation energy to break down bonds and as we are heating the orange juice the energy used to break the vitamin C inter-molecular bonds is heat energy. This is because the bonds holding the vitamin C molecule together are being broken, and the more heat energy available the more vitamin C bonds can be broken. So by increasing the temperature I will expect to need less DCPIP to change the colour of the orange juice to the standard I have chosen (when the solution has turned a purply-brown colour). I predict that when I plot a graph of temperature against volume of DCPIP used, I will get a straight-line, indicating direct correlation between the two. Method: In order that we obtained the most accurate results possible, I conducted a preliminary experiment. ...read more.


All these symptoms come about as a result of the requirement for Vitamin C in the development of the ground substance between our cells. It is this ground substance, primarily collagen, is the cement that gives our tissues form and substance. Collagens are principal components of tendons, ligaments, skin, bone, teeth, cartilage, heart valves, intervertebral discs, cornea, eye lens, as well as the ground substance between cells. Some collagen will form in the absence of ascorbic acid, but the fibers are abnormal, resulting in skin lesions and blood vessel fragility, characteristics of scurvy. A person who is dying of scurvy stops making this substance, and his body falls apart -- his joints fail, because he can no longer keep the cartilage and tendons strong, his blood vessels break open, his gums ulcerate and his teeth fall out, his immune system deteriorates, and he dies. Collagen is a protein, one of the thousands of different kinds of proteins in the human body. Most proteins occur only in small amounts. This is because the various enzymes are so powerful in their ability to trigger specific chemical reactions to take place rapidly that only a gram or two or even a few milligrams may be needed in the body. There are a few exceptions. There is a great amount of hemoglobin in red blood cells. ...read more.


This leads me to believe that either it is anomalous OR that the number of vitamin C molecules slightly increases before decreasing again. As the latter doesn't make sense to me, I have called it anomalous. The 21.2 cm3 I get at 31? in my preliminary experiment is anomalous for the same reason. One reason for possible inaccuracy is that the test tubes appeared to contain condensation after being heated. This is because often the juice was chilled before we used it. This water could have had an effect on our results by diluting the orange juice. This would lower the concentration of the orange juice and the the vitamin C. By lowering the concentration, the vitamin C molecules take longer to react with the DCPIP, which perhaps meant I used too much DCPIP without realising. Had I had time I would simply have bought the orange juice the day before and kept it out of the fridge. I believe my results were fairly accurate but I would hesitate to say faultless. With a short time to collect my results and the preliminary results, I believe I would have obtained more accurate results if I had had more time. I would like to have used the ascorbic acid and measured the amount of DCPIP it needed to turn purply-brown. Then I would have compared it to one of my samples and found out the exact concentration of each sample, instead of making do with finding out the amount of DCPIP needed. I plan to do this if given further time. ...read more.

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