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Osmosis Investigation

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Introduction

Osmosis Investigation Planning The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato as they provide a ready supply of homogeneous material. Osmosis is the diffusion of water molecules across a partially permeable membrane from a high concentration of water to a low concentration of water. My prediction for my experiment is that as the salt concentration gets higher the potatoes will get lighter. I think this because movement of substances takes place through the cell membrane, which separates the different substances in the cell from its surroundings. This type of membrane allows small molecules such as water to pass through it, but it denies entry to particles, such as glucose and salt to pass. So on the no concentration of salt because water will infiltrate the potato it will make it heavier heavier. As the salt concentration gets higher it cannot permeable through and erodes some of the potato instead making the potatoes lighter. ...read more.

Middle

Variables that may affect the experiment (rate of osmosis) - � Concentration of Salt Solution � Size of the potato � Temperature of surroundings � Time I will need to make some precautions for my experiment to make sure that it is fair and I don't get to many anomalous results. I need to make sure I remove all the potato peel of the discs because this will affect how much can penetrate through. Also I need to make sure that I blot dry them before reweighing otherwise sum access water may be on them making them seem heavier. Experiment A Percentage of salt concentration Weight before (g) Weight after (g) Weight change (g) Percentage change % 0 2.68 2.93 +0.25 9.3 1 2.64 2.63 +0.03 1.1 2 2.62 2.38 -0.24 9.2 3 2.65 2.27 -0.38 14.3 4 2.60 2.08 -0.52 20 Experiment B Percentage of salt concentration Weight before (g) Weight after (g) Weight change (g) ...read more.

Conclusion

This type of membrane allows small molecules such as water to pass through it, but it denies entry to salt so there is no way the potato can get any heavier. The salt erodes at the potato instead making it lighter. Evaluation There was one anomalous result in my table and that was in experiment 'A' where on the '1' concentration of salt the potato got heavier when it should of got lighter this may have been because we might not have blotted it probably before we weighed it again. This anomalous result does not matter because on the experiment 'B' we got an accurate result to use as our average. The experiment could have been improved by doing a bigger variety of salt concentrations, left them all for longer and done more than two repeats. These points need to improved to get much more accurate results that will make the test a lot fairer. If I did improve these few things my prediction and conclusion would still be correct but my results would just be a lot more accurate. ...read more.

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