Potato Osmosis Lab

Different Percentages of Sugar Solutions and Their Effect on Potato Weight

Introduction

The experiment was centered on the question: What is the concentration of sugar in a potato? This question is an important one to understanding how we digest potatoes and could be used for nutritional information. In order to find the answer to this question we cut a potato into 5 pieces, placing each in a different solution of sugar and water of about 150ml. Then we waited 30 minutes to see if the effects were hypotonic or hypertonic, giving us a reasonable percentage to how much sugar a potato has naturally. We predicted that the solutions with 0%, 1% and 5% sugar would create a hypotonic environment, increasing the weight of the potato pieces. While the 10% and 15% solutions would create a hypertonic environment, causing the potato to lose weight. This assumes that a potato is naturally between 5% and 10% sugar.

Materials and Methods

Materials

5 Beakers

150ml Pure Water
150ml 1% Sugar Solution
150ml 5% Sugar Solution
150ml 10% Sugar Solution
150ml 15% Sugar Solution
Scale
Russet Potato
Potato peeler
Knife
Cutting board
Ruler
French fry cutter

Methods
Pick a russet potato and peel it, then use the French fry cutter to cut it into at least five rectangular pieces.

Trim these pieces to 5cm long each. Weigh each piece of potato and record the initial weight. Fill the five beakers with each different solution: 0%, 1%, 5%, 10%, and 15%. Mark which piece is going in which beaker and place all five potato chunks into separate beakers. Let sit for 30 minutes. Remove potato chunks and weigh them, record final weight of each piece. Use the formula; % change = (Final mass- initial mass)/Initial Mass X 100 to get the percentage of change in weight in each potato piece.

Results

The potatoes in solutions 0% through 10% all gained weight, meaning they were in a hypotonic environment. The potato piece in the 15% solution lost weight, meaning its environment was hypertonic. This means that a potato is more than 10% sugar but less than 15%. As you can see on the graph below the estimated sugar content of a potato is around 13%.

Discussion
Our data shows that potatoes in solutions 0% through 10% were in hypotonic environments, while the potato in a solution of 15% sugar was in a hypertonic environment. From this information we can conclude that a potato’s isotonic environment would be a solution of approximately 13% sugar because that is around where the change in weight of the potato hits zero. Our original prediction was slightly wrong, in that we thought the isotonic environment would be between 5% and 10%. Contamination may have been a problem in this experiment, there was a lot of hustle and bustle within the classroom, meaning that everything may not have been kept perfectly clean. The next step for this experiment would be to do a meta-analysis of all the experiments from this class and other classes performing the same experiment. This would give you a more exact percentage of sugar in a potato and show validation for these claims. One could also make solutions of sugar in between 12% and 13% to try to get a more exact percentage of sugars in a potato. Our prediction was proved wrong, but now with more knowledge we could go back and find a more precise answer to our initial question. The experiment could be improved by adding more solutions between 10% and 15% to get a more precise percentage of sugars in the russet potato. Also it could be regulated better to discourage any contamination that may have happened. This experiment could be used with a wide variety of vegetables to determine their sugar percentage.