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Introduction

Sabina Narloch 3IB November 4, 2009 Warsaw 33 Liceum im. M. Kopernika THE EFFECT OF SALT SOLUTION ON OSMOSIS IN DE-SHELLED EGGS Working partner: Oktawia Sosnia INTRODUCTION Osmosis is the transport of water molecules from an area of their high concentration (hypertonic solution) to an area of their low concentration (hypotonic solution) through a semi-permeable membrane1 such as cell membrane. This tendency, when water molecules move from one region to another is called the water potential2. Osmosis is also called the passive movement so it does not require energy as direction of transport is down the concentration gradient3. What is important, the movement of water molecules occurs until the state of equilibrium, so-called isotonic environment, is reached. Thanks to process of osmosis, an egg will shrink or enlarge depending on the saturation of the solution of the surrounding. The process of osmosis will cause an egg to shrink after its submergence in solution with lower concentration of water and higher concentration of solute outside (hypertonic), respectively, an egg will enlarge after its displacement in solution with greater concentration of water and lower concentration of solute outside (hypotonic). In this experiment, de-shelled quail's egg will be submerged in three different liquids: distilled water, 5% salt (NaCl) solution and 10% salt solution, thus the aim of the investigation is to observe process of osmosis and changes in eggs' masses connected with it, in different solutions. As it was already mentioned, eggs' shells were dissolved (in hydrochloric acid) in order to attain more reliable results. HYPOTHESES * Solvent will diffuse inside the egg as during osmosis, water molecules move from hypotonic solution to hypertonic solution * The greatest mass change will occur in set where an egg is immersed in distilled water as there is the greatest difference in substances dissolved in water RESEARCH QUESTION How does the mass of an egg will change after submergence in distilled water and solutions that differ with salt concentration? ...read more.

Middle

Range - the difference between maximum and minimum value 5. The formula for calculation of standard deviation () 6. The formula for calculation of change in mass after immersion for particular time 7. The formula for calculation of mean change in mass of eggs 8. The formula for calculating percentage change in mass in overall PROCESSED DATA Table 2. Statistical analysis for the sets measured before measurement (to 6 s.f.) set 1 set 2 set 3 SD 1.37719 0.625504 0.985423 mean 11.2067 11.5167 11.4550 mode - - - median 11.3000 11.4550 11.7800 range 4.32000 2.05000 2.49000 Table 3. Statistical analysis for the sets measured after 30 minutes (to 6 s.f.) set 1 set 2 set 3 SD 1.80301 0.596315 0.996995 mean 12.1083 11.7150 11.3300 mode - - - median 11.7600 11.6650 11.6350 range 5.41000 1.96000 2.52000 Table 4. Statistical analysis for the sets measured after 1 hour (to 6 s.f.) set 1 set 2 set 3 SD 1.94292 0.622218 0.999790 mean 12.5467 11.9367 11.4317 mode - - - median 11.9500 11.8700 11.7750 range 5.70000 2.02000 2.50000 Table 5. Changes in mass presented in grams and percentages (calculated from means presented in Tables 3-4) specification change in mass in set1 [g; �0.01g] % change in mass for set1 change in mass in set2 [g; �0.01g] % change in mass for set2 change in mass in set3 [g; �0.01g] % change in mass for set3 before - after 0.5h +0.90 +8.03 +0.20 +1.74 -0.13 -1.13 before - after 1h +1.34 +11.95 +0.42 +3.65 -0.03 -0.26 Note that in all graphs presented below, set 1 is a set with distilled water, set 2 is a set with 5% salt solution, set 3 is a set with 10% salt solution. Graph 1. Mean results for all of the measurements with error bars Graph 2. Mean percentage changes in mass after 30 minutes with trendline and error bars Graph 3. ...read more.

Conclusion

* On some eggs, the shell did not completely dissolved, it reduced (but insignificantly) the side, or to some extent rate of osmosis process * Some students did not wipe eggs carefully before measurement of eggs' mass (s) * Some students did not put eggs (after measurement) at the same time, so the time that was measured after submergence was not equal what affected results (s) * The air cells in eggs hindered complete immersion of the eggs (s) * Because of air cell, test tubes were used in order to hold the eggs under water, but it was quite dangerous as semi-permeable membrane is very delicate, what is more, because of the region were test tube contacted membrane, the surface of osmosis process was reduced * Some students did not even try to immerse the eggs completely (s) * While pouring salt solution, measuring cylinders with different accuracy were used because there was not enough time for carrying out the experiment * While drawing the graphs, the trendlines were not drawn as it made the image unclear Advantages * In our class, one person prepared salt solutions so there was no probability that someone while preparing solutions for her/his group would make a mistake while measuring water either salt * Electronic balance with accuracy �0.01 g was used, it made results more reliable * Statistically, enough measurement were carried out * Type, origin, condition and size of the eggs were controlled so the results were more reliable * Safety precautions were taken while using hydrochloric acid in part of dissolving eggs' shells * Based on range, collected data are good quality * Egg's shell was dissolved, left semi-permeable membrane was excellent for the experiment as it is flexible and very thin Suggestions of improvements: * The experiment should last longer (e.g. 5 hours)in order to find out how mass of the eggs will change later * It would be good if more kind of solutions (i.e. not only salt but e.g. ...read more.

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