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Osmotic pressure and water

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Introduction

Osmotic pressure and water potential Raw data (mol/l) SUCROSE APPLE PIECES (cm) SIZE/LENGTH BEFORE/AFTER AVERAGE LENGTH B / A (g) MASS BEFORE /AFTER AVERAGE MASS B / A 0 1 5.0 / 4.7 5.0 / 4.76 5.95 / 2 5.0 / 4.9 6.52 / 3 5.0 / 4.7 6.28 / 0,2 1 5.0 / 4.7 5.0 / 4.66 5.89 / 2 5.0 / 4.7 5.48 / 3 5.0 / 4.6 6.29 / 0,4 1 5.0 / 4.9 5.0 / 4.8 5.78 / 2 5.0 / 4.7 6.09 / 3 5.0 / 4.8 6.44 / 0,6 1 5.0 / 4.8 5.0 / 4.76 5.98 / 2 5.0 / 4.8 5.90 / 3 5.0 / 4.7 6.00 / 0,8 1 5.0 / 4.8 5.0 / 4.76 5.45 / 2 5.0 / 4.7 6.65 / 3 5.0 / 4.8 6.57 / 1 1 5.0 / 4.8 5.0 / 4.83 6.91 / 2 5.0 / 4.8 6.79 / 3 5.0 / 4.9 6.61 / Results / Data We put samples of apple and potato tissue in 6 different sucrose solutions of different molarities; we measured the change in mass. ...read more.

Middle

The average mass and length values (B/A = before/after) Explanation and conclusion: Average masses and lengths may not be accurate enough because we did not get accurate results in our measurements. The mass was supposed to be lower at a higher concentration, but it is not always like that. We cannot be sure about these results and we would maybe have to repeat this experiment and take much more representative sample. The results were supposed to show that the mass gets lower at a higher concentration of solution and it grows at the value 0,0. They do not confirm the theory. According to theory, osmotic pressure can be regarded as the tendency of solution to gain water across an ideal partially permeable membrane. The osmotic pressure depends on its solute concentration. It follows that a solution with a high osmotic pressure has a low water potential. In our case, the water potential is the highest at 0% concentrated solution. ...read more.

Conclusion

The color changed from orange to very dark orange. When we put benedict's solution into small amount of potato with distilled water and heated the test tube in hot water it turned out that there is not so much sugar in it. The color changed from orange to green-yellow. We can conclude, that benedict reduces sugar and causes a change of color. Test 2 (determining starch) Iodine: Iodine solution is used to identify the presence of starch. The solution is yellow-brown but, when it reacts chemically with starch, a blue-black substance called iodide starch is produced. When we put few drops of iodine solution in each test tube and in apple tissue it turned out to be less starch than in potato. That is because apple has pectin and not starch. The color of apple changed from orange to brown, and in potato it changed from yellow to blue-black. APPLE POTATO Before After Before After Iodine solution Iodine solution ORANGE BROWN YELLOW BLUE-BLACK Benedict's solution Benedict's solution ORANGE DARK ORANGE YELLOW GREEN-YELLOW by Marija Galinec IB1 ...read more.

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