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Osmosis and diffusion experiments

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Introduction

Title : osmosis and diffusion ntroduction: Cells have kinetic energy. This causes the molecules of the cell to move around and bump into each other. Diffusion is one result of this molecular movement. Diffusion is the random movement of molecules from an area of higher concentration to areas of lower concentration. Osmosis is a special kind of diffusion where water moves through a selectively permeable membrane (a membrane that only allows certain molecules to diffuse though). Diffusion or osmosis occurs until dynamic equilibrium has been reached. This is the point where the concentrations in both areas are equal and no net movement will occur from one area to another. If two solutions have the same solute concentration, the solutions are said to be isotonic. If the solutions differ in concentration, the area with the higher solute concentration is hypertonic and the area with the lower solute concentration is hypotonic. Since a hypotonic solution contains a higher level of solute, it has a high solute potential and low water potential. This is because water potential and solute potential are inversely proportional. A hypotonic solution would have a high water potential and a low solute potential. An isotonic solution would have equal solute and water potentials. Water potential (?) is composed of two main things, a physical pressure component, pressure potential (?p), and the effects of solutes, solute potential (?s). A formula to show this relationship is ? ...read more.

Middle

The molarity of the sucrose in the bag determines the amount of water that either moves into or out of the bag, which changes the mass. For example, when the bag contained a 0.2M solution, water entered the bag to make the concentrations inside and outside of the bag more equal. As this happened, the mass rose 1.2g 2) If each of the bags were placed into a 0.4M solution instead of distilled water, the masses of the bags would have changed in different ways. The mass of the bags filled with distilled water and 0.2M sucrose would have gone down because water would have left the bag. The mass of the 0.4M bag would have stayed the same because the concentrations are now equal. The masses of the 0.6, 0.8, and 1.0M bags would have increased because water would have moved into the bag to equalize the concentrations. 3) In the data collected, the percent change in mass was calculated to show how greatly the mass increased or decreased. The difference in mass is not enough to go by because the initial masses of the dialysis bags were not all the same. 4) If a dialysis bag's initial mass was 20g and it's final mass was 18g, the percent change in mass is 20%. 5) The sucrose solution in the beaker would have been hypotonic to the distilled water in the bag. Lab 1C Table 1.4 Contents of Beaker Initial Mass Final Mass Difference in Mass % Change in Mass Initial Temp. ...read more.

Conclusion

If the onion cell experiment in part 1E of the lab would have produced correct results, conclusions could have been made. It is thought that the onion cells would have plasmolyzed due to the addition of NaCl to the cells. This shows how the onion cells had high water potential and moved to the area outside the cell with lower water potential. Then, after adding water back to the cells, water would have moved back into the cells increasing turgor pressure. The water potential played an enormous role in each part of this lab. Since water moves areas of high water potential to areas of low water potential, reactions took place in each part resulting in different conclusions being derived from them. Water potential was a key element in each part of the experiment. In plant and animal cells, loss or gain of water can have different effects. In a plant cell, it is ideal to have an isotonic solution. If the solution is hypertonic, the cell will shrivel from lack of water intake. Inversely, if the solution is hypotonic the cell could take in too much water and the cell will lyse and break open. For a plant cell, the ideal solution is a hypotonic solution because the cell takes in water increasing turgor pressure which keeps the cells tightly packed and keep their shape. If the solution is hypertonic, the cell will plasmolyze and died from lack of water. In an isotonic solution, the plant cell does not have enough turgor pressure to keep is shape. ...read more.

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