Osmosis and potatoes

[nikaelalarge]

I completed an experiment regarding osmosis, potatoes, food dye and surface area.
Basically there were 4 beakers, each with 15g of table salt, 3 drops of red food dye, 300mL of water and a potato. Each weighing 59g and cut into different size cubes. A whole cube, one cut into halves, one cut into quarters and one cut into eighths.
The experiment was left to sit for 5 days. It was checked and weighed on the third day, all the potatoes had lost weight and had started to become squishy to touch but other then that no shocking results were seen. When checked again on the fifth day all the coloring from 3 of the beakers was completely gone (the beakers with the halves, quarters and eighths) the beaker with the whole cubes's water remained red. When the potatoes were cut open the potatoes that food dye disappeared from their beaker were slightly pink in the middle and potato colored on the outside and they all lost weight. The whole cubed potato however when cut open was red on the outside but potato colored in the middle and gained weight from when it was weighted on day 3. Can you explain this? Is it possible or have my results been tampered with? Please help!!!

[SciB]

Hi,

I think your results are reasonable. The smaller you make the potato the more surface area there is to absorb the food dye. Also, as time passes small bits of the potato will dissolve in the water making the pieces weigh less than the starting weight of 59 g.

You said that the whole cube of potato weighed more at the end of 5 days. How much more? How did you weigh the pieces? Did you let them dry first? If so then the smaller pieces may have lost more weight due to water evaporation than the large piece.

I would not expect the whole potato cube to gain weight unless it soaked up some water. You used the same weight of potato in each case but did the pieces all come from the same potato? If not then there may have been some variation in the age or flesh of the potato that might account for the weight gain.

Just report what you found in your experiment and make your best guess as to what happened. When you do an experiment, it improves the statistics if you do at least three samples for each test. You should have set up 12 beakers with salt and dye so you could have 3 readings for each sample. Being able to take the average of 3 weights would have allowed you to calculate the standard deviation which is an important statistical parameter that you can use to prove whether or not there really is a difference among your samples. Keep this in mind when you do your next science project.

Sybee