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Investigating the Rate of Osmosis.

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Introduction

Investigating the Rate of Osmosis Introduction Osmosis is the diffusion of liquid molecules through a partially permeable membrane. The liquid molecules from the high concentrate go into the low concentrate of liquid. Osmosis occurs in the intestine, which is the semi-permeable membrane. Osmosis occurs in the body at approximately 37�C. Hypothesis Osmosis is a special type of diffusion. It is the diffusion of water from where there is a high concentrate of water molecules (the weaker solution of sugar) to where there is a low concentrate of water molecules (the stronger sugar solution). In this experiment, because there is less sugar in the potato than in the solution around it, I will expect the potato to have a loss in mass after the experiment. This is because the water from the potato diffuses through the membrane to the higher concentrate of sugar to try and make it equal. Sugar molecules are too big to diffuse through the membrane. Water particles gain kinetic energy when heated therefore there is more diffusion taking place. At lower temperatures for example 10�C, I expect the potato to loose the least mass and at higher temperatures for example 50�C, I expect the potato to loose the most mass. If I used a temperature as high as 60�C the outside of the potato may disintegrate. If I were to use visking tubing I would expect that when the water leaves, the external pressure will force the tubing inwards. ...read more.

Middle

* Jewellery will be removed to prevent it from getting in the way. * Hair will be tied back. Results Preliminary results Test tube Temperature (�C) Initial Mass (g) Final Mass (g) Mass Change (g) % Mass Change A 10 3.7 3.5 -0.2 5.7 B 20 4.0 3.7 -0.3 8.1 C 30 4.0 3.6 -0.4 11.1 D 40 4.0 3.6 -0.4 11.1 E 50 4.0 3.6 -0.4 11.1 Preliminary results are taken to get useful results. Useful results are results that match the prediction. In this case the results above do match my prediction and as the temperature increased mass was lost. The experiment will be repeated twice more and the results displayed below. 1st set of results Test tube Temperature (�C) Initial Mass (g) Final Mass (g) Mass Change (g) % Mass Change A 10 2.7 2.7 0 0 B 20 3.2 3.2 0 0 C 30 2.8 2.6 -0.2 7.7 D 40 3.0 2.8 -0.2 7.1 E 50 2.8 2.5 -0.3 12 2nd set of results Test tube Temperature (�C) Initial Mass (g) Final Mass (g) Mass Change (g) % Mass Change A 10 1.0 0.9 -0.1 11.1 B 20 1.0 0.9 -0.1 11.1 C 30 1.0 0.9 -0.1 11.1 D 40 1.0 0.9 -0.1 11.1 E 50 0.9 0.8 -0.1 12.5 Overall results averaged Test tube Temperature (�C) Initial Mass (g) Final Mass (g) ...read more.

Conclusion

If the water bath's temperature was slightly higher that 10�C slightly more mass would have been lost causing it to be rounded up instead of down. The method is fairly easy and obtaining the results is also easy. Rounding proved a problem because I only rounded it to one decimal place causing inaccurate results. If I were to do it again I would make sure the water bath is at the right temperature and measure it with a thermometer. I would also round to three decimal places. To be more accurate when weighing I would make sure the scales are completely dry and the potato is as dry as possible. Enough results were taken to make a conclusion and for each experiment the results matched my prediction. The results would have been even clearer if I'd have rounded to two or three decimal places. To extend the experiment a wider range of temperatures could have been used. For instance 0�C-60�C. 0�C is the freezing point so it would be interesting to see if osmosis does occur at freezing point. At 60�C I stated that the outside of the potato would disintegrate leaving no semi-permeable membrane. Using 60�C would prove this. If you were to use the capillary tube method it would measure the loss of water not the mass. I chose not to do this method however because it was quite difficult and needed more than one person to tie the visking tube to the capillary tube. ...read more.

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