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IB BIOLOGY INTERNAL POTATO OSMOSIS

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Introduction

Aim: To investigate the effect of changing solute concentrations on the process of osmosis in potato chip of a given size. Hypothesis: I predict that as the solute concentration increases, the mass of the potato will decrease because due to osmosis, water has the tendency of flowing to an area of low concentration from an area of high concentration, and as the solute concentrations increase, there will be a lower concentration of water in the solution, hence the potato mass will decrease. The independent variable in this experiment will be the solute concentrations. Water and sugar solutes of 0.1, 0.3, 0.6 and 0.8 mols -1 will be used in the experiment The dependent variable in this experiment will be the mass of the potato chips after osmosis compared to before the osmosis. There are several controlled variable worth mentioning. Make sure all potato chips used are of the same length, by measuring each with a ruler. Use only solid, whole potato chips, check the solidity by observing each chip. Measure the quantity of solutes used with a measuring cylinder, and measure at eye level to obtain accurate measurements, use the same amount of solute for all types of concentrations. Control the time period allowed for osmosis, by timing with an electronic timer from the exact moment the chips are placed in the solutes. ...read more.

Middle

Mass after osmosis (gram) Mass after osmosis (gram) Type of Solute Blue Red White 1 1.205 1.202 1.201 water 2 1.022 1.078 1.029 sugar 0.1 mol-1 3 1.087 1.095 1.096 sugar 0.3 mol-1 4 1.011 1.027 1.046 sugar 0.6 mol-1 5 0.943 1.059 0.964 sugar 0.8 mol-1 Percentage Mass Change Type of solute Initial Mass in grams Final Mass (after osmosis) in grams Mass Difference Percentage mass change (5sf) Water 1.179 1.205 0.026 2.2053% 1.173 1.202 0.029 2.4722% 1.174 1.201 0.027 2.2982% sugar 0.1 mol-1 0.095 1.022 0.927 975.79%(outlier) 1.064 1.078 0.014 1.3158% 1.015 1.029 0.014 1.3793% sugar 0.3 mol-1 1.090 1.087 -0.003 -0.27523% 1.108 1.095 -0.013 -1.1733% 1.105 1.096 -0.009 -0.81447% sugar 0.6 mol-1 1.063 1.011 -0.052 -4.8918% 1.069 1.027 -0.042 -3.9289% 1.096 1.046 -0.05 -4.5620% sugar 0.8 mol-1 1.003 0.943 -0.06 -5.9820% 1.134 1.059 -0.075 -6.6138% 1.015 0.964 -0.051 -5.0246% Average Percentage Mass Change Type of solution Average Percentage Mass Change (4sf) Water 2.325% sugar 0.1 mol-1 1.348% sugar 0.3 mol-1 -0.7543% sugar 0.6 mol-1 -4.461% sugar 0.8 mol-1 -5.873% Average Percentage Mass Change Graph Conclusion: To begin we need to understand the meaning of Osmosis. Osmosis is the diffusion of molecules through a semi-permeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal. The results above confirm the meaning of Osmosis and it makes the hypothesis correct. ...read more.

Conclusion

This may have caused inaccuracies in the measurements of the mass of the potato chip. Modifications: There are definite improvements that could benefit the validity and accuracy of the experiment. When the potatoes are being dried, a timer should be used to time for one minute, which is the time allowed for the drying process. This provides an adequate time period for the potato chips to dry. By timing the process, it makes the experiment fair and reinsures that the potatoes all received the same amount of time to dry. A whole potato should be used in future experiments. This ensures that all the potato chips obtained, are wholesome and solid, instead of the soft crumbly bits of potato used in this experiment. The chips should also be cut with a sharp knife and a ruler, to ensure they are all the same size. Both of this steps will ensure the potato chips are equal in surface area, other wise osmosis could occur father in one chip than the other. The removal of the potato chips should be done with a sterile tong, to ensure each potato chip receives the same treatment of removal. Without this process, the mass of the potato chips after removal from the solutions, may be inaccurate. If time allows, the recording of all the data should be repeated on two separate sheets of paper, to increase accuracy, and to act as a back up to the other. Without a back up, the data could be easily destroyed, and the experiment may become completely inaccurate. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

***
A sound investigation in to the effect of varying solute concentrations on the mass change of potato chips due to osmosis.

The introduction was a bit brief and did not really identify the scientific theory upon which the report could be based, this was included in the conclusion but was less effective at the end.

The method was a little vague in some areas. It should enable the reader to repeat the experiment after reading. Remember to explain all steps in sufficient detail.

The conclusion was good and made sound links to the data, and scientific theory and linked in well with the hypothesis.

Marked by teacher Jon Borrell 22/05/2013

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