Determining the Solute Concentration of Potatoes
Asif Nazerally,
Monica H.-S., Tashiana L., Leah B.
B. C. Boivin
Abstract
The purpose of this experiment was to experimentally determine the solute concentration of Russet potatoes. Four-centimetre pieces of potatoes were inserted into six solutions containing different concentrations of sucrose in water. The solute concentration for russet potatoes were determined to be BLANK. This method could be used to determine the solute concentration of everyday food products.
SBI 4UE, Grade 12 University Biology, Rockland District High School
Friday, March 21th, 2013
Introduction
In this experiment, the solute concentration of russet potatoes will be determined. The word “russet” actually means “rough”, so most potatoes can be classified as a “russet” potato, but nowadays, in North America (where they are very popular), a russet potato actually refers to a russet Burbank potato, for its taste and texture (Anonymous, What is a russet potato?, 2012). Although they are not growing, their cells are still alive, with semi-permeable membranes that O2, CO2, H2O and lipid-soluble molecules can pass through (Boivin, 2014).
There are three different types of solutions, in terms of solute concentrations; hypertonic, hypotonic, and isotonic. Explain these.
Osmosis is the process in which a solvent (i.e. water) passes from a solution with a low solute concentration to a solution with a high solute concentration (Bowen, 2000). The reason that the water runs at all is because it can pass through cell membranes, and the reason it runs against the concentration gradient is so that it may dilute to the concentrated solution, in an effort to make the two solutions isotonic (O'Loughlin, 2006). The reason why your fingers would dry out after swimming in salt water is due to osmosis: water leaves your fingers to dilute the salt water.
The purpose of this experiment is to use six different solutions with different solute concentrations of sucrose in water to experimentally determine the solute concentration of russet potatoes.
Materials and Methods
The materials and methods used were that of the Measuring Potential and Kinetic Energy using a Pendulum handout on November 7nd, 2012.
Results and Observations
Table 1. Determining potential energy of the pendulum.
Mass (kg) / Drop Height (m) / Potential Energy, Eg (J)[Eg=mgh]
0.05 / 0.41 / 0.2
0.200 / 0.46 / 0.9
0.500 / 0.51 / 2.5
Table 2. Determining kinetic energy of the pendulum.
Mass (kg) / Distance Travelled for One Swing (m) / Time for 20 Complete Swings (secs.) / Period(secs.)
[time/20] / Average Speed, v (m/s) / Kinetic Energy, Ek (J)
[Ek=12mv2]
0.05 / 3.2 / 36.8 / 1.84 / 1.739 / 0.0756
0.200 / 3.6 / 36.2 / 1.81 / 2.011 / 0.4044
0.500 / 4.0 / 39.9 / 2.00 / 2.004 / 1.0045
Discussion
It was determined mathematically that the potential energy was 0.2J for the 50g weight, 0.9J for the 200g weight and 2.5J for the 500g weight. It was then determined experimentally that the kinetic energy was 0.0756J for the 50g weight, 0.4044J for the 200g weight and 1.0045J for the 500g weight, after twenty complete swings of the weights. These results appear to be inaccurate due to the large margin of possible errors, primarily that the pendulum lost a great deal of momentum and energy due to the instability of the pendulum.
There were many possible sources of errors throughout this experiment. One of them would be that a lot of the potential energy is being lost through the pendulum. The reason is because the pendulum being used were quite old, therefore unstable and wobbly, and making the results of the experiment inaccurate. A possible solution to this would be to perhaps invest in more modern or reliable equipment or to clamp down the pendulum (but that would still leave the upright pole unstable).
Another possible source of error would be the energy lost in the string. The string that the weight was hung from was tied around a metal ring, which was attached to the pendulum. When one of the heavier weights were used, the string was susceptible to sliding, which would render the results inaccurate since there is energy being lost. A solution to this issue would be to tape down or glue down the string to the metal ring.
A third possible source of error could be that the desks that the pendulum stood on were uneven or crooked, thus making the swinging difficult to go one way and easier to go the other. To fix this issue, the desk’s legs could have been measured until they were made even. All of these possible sources of error could have negatively affected the results of this experiment.
Calculations
% of Difference for 50g weight
% of Difference= Eg- EkEg x 100%
% of Difference= 0.2- 0.07560.2 x 100%
% of Difference= 62%
% of Difference for 200g weight
% of Difference= Eg- EkEg x 100%
% of Difference= 0.9025- 0.40440.9025 x 100%
% of Difference= 45%
% of Difference for 500g weight
% of Difference= Eg- EkEg x 100%
% of Difference= 2.5- 1.00452.5 x 100%
% of Difference= 60%
Conclusion
Questions
1. Calculate the percentage difference between Eg and Ek for the mass that gave you the most precise results (closest) using the formula: % of Difference= Eg- EkEg x 100% . Ensure that you comment about how precise you feel this value is.
(Please refer to the ‘Calculations’ section on page 5)
I feel that the percentage of difference is quite accurate due to the amount of energy lost to the unstable pendulum and the slight movement of the string (please refer to the ‘Discussions’ section on page 4 for more details on sources of error).
2. Calculate the percentage difference between Eg and Ek for the mass that gave you the worst results (furthest) using the formula from the previous question. Ensure you comment about how precise you feel this value is.
(Please refer to the ‘Calculations’ section on page 5)
I am not sure why the smaller weight would attract more inaccurate results than the larger weights, because the larger weights should cause the pendulum to wobble and shake more, taking energy away from the swinging itself. I do feel that the percentage of difference is accurate because there were many sources of errors to take into account like the instability of the pendulum (please refer to the ‘Discussions’ section on page 4 for more details on sources of error).
3. List a few sources of error that you feel could have affected your results.
(Please refer to the ‘Discussions’ section on page 4)
Selected References
Anonymous. (2011, February 11). Physics . Retrieved November 13, 2012, from Wikibooks: http://upload.wikimedia.org/math/4/7/0/470ec22866c4b54b959c8559cd27c25d.png
Anonymous. (2012). What is gravitational energy definition? Retrieved November 13, 2012, from Answers: http://wiki.answers.com/Q/What_is_gravitational_energy_definition
Anonymous. (2012). Work, Energy, and Power. Retrieved November 13, 2012, from The Physics Classroom: http://www.physicsclassroom.com/class/energy/u5l1b.cfm
Rudeen, S. (2012, November 7). Physics 11/12 2012. Retrieved November 12, 2012, from Facebook: http://sphotos-a.ak.fbcdn.net/hphotos-ak-ash3/533604_10151129833702810_1480149778_n.jpg