Day 4 -- A Starchy Situation

Daniel and I tried our hands at explaining diffusion and osmosis, only this time, there were no words allowed. (Besides "diffusion" and "osmosis") I decided to take the mature path, while Daniel attempted to explain diffusion through a different... type of expression.

We jumped right into the first experiment today. Daniel and I attempted to identify the concentration within six liquids of different colors. We placed 8mL of each liquid into a permeable membrane, tied them off, and dropped them into 30mL of distilled water. You can see the initial sizes, as well as the results after 30 minutes, in the pictures below.

Initial dialysis tubing size

Size after 30 minutes

The results, as well as the approximate molarity of each of the liquids, were easily interpreted after the experiment. The red and green liquids showed a massive amount of change in comparison to the others. Through the newly-learned process of osmosis, the water diffused through many of the membranes into the area of fewer water molecules. (As shown on the board.)

Then we split the group up. While our group attempted to do a similar problem using slices of potatoes, our lab partners tested the best molarity of sports drinks. We obtained some sliced potatoes and surgically cut them into roughly-equal pieces. After massing the potatoes and placing them in colored liquids, we allowed nature to take its course.

I came to the lab late last night to measure the potatoes in the liquid. Although it seems that our data was acceptable (in both experiments) it was still relatively off. Some of the potatoes that I predicted to shrink ended up growing, and vice versa. (I guess it isn't about being correct, it's about the final result.) The results can be explained through the processes of osmosis and diffusion. As water tends to move from high water concentration to lower concentrated areas (places with more solution and less water), we can predict the molarity changes by the mass changes...

Red potato data (Left) vs. Molarity (Right)

Graph of potato molarity (Not the Red potato data)

The average mass changes for the blue and clear were positive, meaning water seeped out the system. For the others, however, there was a negative mass change, suggesting that the water went into the system. Because the isotonic point fell between 0.2M (Clear) and 0.4M (Green) in the results, we the isotonic point of the potato is between the two. 

When we graphed the results, we discovered that it was a bit more than 0.2M for the red potato. The graph that Daniel and I made for the solution doesn't reflect the data above, but the different type of potato. (Seen above)

Similarly, an experiment was done to test the solute percentage of energy drinks. Just like the original dialysis tube experiment, four different energy drinks were placed in dialysis tubing. The six tubes were then placed in six cups, just like the potato experiment (shown above). 

Now, the doctor is called in for a case. An 18-year-old teenager