The Grand Experiment pt. 3
I have been holding back long enough. It is now time to go back and talk about the Grand Experiment. Now if you don't remember this was a three step process.
Step 1: Come up with a Question
Step 2: Design an Experiment
Now my lab partner and I chose the titration of Vitamin C. Each lab class was given 3 weeks through the semester to work on the Grand Experimental Challenge. The first week was spent figuring out what the lab procedure was going to be and what materials were needed. My partner and I decided to test the Vitamin C in Grapefruit juice and apple juice and their respective concentrates. We were looking up different titrations online and trying to figure out which one was the best for us to do. We found one, told our instructor which chemicals we were going to need from the stock room and which materials were needed as well. We of course had to provide the juices ourselves.
So two weeks later came, and we were walking to lab with juice in our hand. We had tried to get the same brand of juice thinking that it would make them easier to compare or something, but my problem was that I couldn't find the apple juice concentrate to save my life, so I ended up buying organic apple juice which had no ascorbic acid in it (which is what we were looking for).
Now on the day of the experiment we were all ready to go with what we had planned out and the experiment we chose. Then to learn there was a lab made up for us, I guess that makes it easier because of the materials required are all the same, since there were a couple people in the class testing vitamin C, they were just using different products like oranges and orange juice instead.
We had four different solutions to make before we could actually start our titration. There was a potassium iodate solution which was what was used to titrate the juices, a potassium iodide solution and a sodium hydroxide solution that were both added to the juices in the flask, and a starch indicator solution which was used to indicate when the solution was done titrating.
Now here comes the fun part, well, actually not really. Our first couple trials seemed to be malfunctioning. We started out using the apple juices as our unknowns. The problem was that we could put one drop of the potassium iodate solution (liquid sitting in the burette above the flask) and it would immediately change. Just in case you were wondering that isn't exactly what is supposed to happen, not with a single drop at least. So we tried again. And the same thing happened. What was going on, we didn't actually know. We weren't sure if it was the brand of juice or the type of juice, so we tried the organic apple juice concentrate. But the same thing happened, barely a drop of the potassium and the unknown changed in an instant.
A short chat with our professor later and a look at the ingredients and we realized what the problem was. The apple juice was not a good source of Vitamin C which is why it was changing immediately because there wasn't anything there to be tested. She came over helped us with a trial for our grapefruit juice and it worked perfectly. Thank goodness. What we learned and had actually forgotten about what that the ascorbic acid we didn't want in our juices was actually what we were testing for. The scientific name for Vitamin C is ascorbic acid. Whoops!
After our little hiccup we ran about 6 different trials for the two different grapefruit juices and got some good data collected. The thing about a titration is that you add so much of a solution into your unknown and along the way have to swirl it around some. If you have done the titration correctly the unknown in the flask should change a color. In this specific titration we were looking for a dark purple/blue change in color through out the entire thing. Its one thing to have a blue spot on top of everything, but if it disappears within a few seconds you aren't done you want to make sure it isn't going to change back to its original color.
Step 1: Come up with a Question
Step 2: Design an Experiment
Step 3: Perform an Experiment
I have to say I don't actually know if my experiment was chosen to be done. We weren't exactly told, and I would think that different lab classes had different experiments to perform. My experiment wasn't on the sign up form in my class, but I do hope it was picked.
Now my lab partner and I chose the titration of Vitamin C. Each lab class was given 3 weeks through the semester to work on the Grand Experimental Challenge. The first week was spent figuring out what the lab procedure was going to be and what materials were needed. My partner and I decided to test the Vitamin C in Grapefruit juice and apple juice and their respective concentrates. We were looking up different titrations online and trying to figure out which one was the best for us to do. We found one, told our instructor which chemicals we were going to need from the stock room and which materials were needed as well. We of course had to provide the juices ourselves.
So two weeks later came, and we were walking to lab with juice in our hand. We had tried to get the same brand of juice thinking that it would make them easier to compare or something, but my problem was that I couldn't find the apple juice concentrate to save my life, so I ended up buying organic apple juice which had no ascorbic acid in it (which is what we were looking for).
Now on the day of the experiment we were all ready to go with what we had planned out and the experiment we chose. Then to learn there was a lab made up for us, I guess that makes it easier because of the materials required are all the same, since there were a couple people in the class testing vitamin C, they were just using different products like oranges and orange juice instead.
Now here comes the fun part, well, actually not really. Our first couple trials seemed to be malfunctioning. We started out using the apple juices as our unknowns. The problem was that we could put one drop of the potassium iodate solution (liquid sitting in the burette above the flask) and it would immediately change. Just in case you were wondering that isn't exactly what is supposed to happen, not with a single drop at least. So we tried again. And the same thing happened. What was going on, we didn't actually know. We weren't sure if it was the brand of juice or the type of juice, so we tried the organic apple juice concentrate. But the same thing happened, barely a drop of the potassium and the unknown changed in an instant.
A short chat with our professor later and a look at the ingredients and we realized what the problem was. The apple juice was not a good source of Vitamin C which is why it was changing immediately because there wasn't anything there to be tested. She came over helped us with a trial for our grapefruit juice and it worked perfectly. Thank goodness. What we learned and had actually forgotten about what that the ascorbic acid we didn't want in our juices was actually what we were testing for. The scientific name for Vitamin C is ascorbic acid. Whoops!
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