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To investigate how different concentrations of the sucrose solution can affect the rate of osmosis, using a potato and different concentrations of sucrose solution and measuring the length of the potato chips to discover their osmotic potential

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Introduction

Aim: To investigate how different concentrations of the sucrose solution can affect the rate of osmosis, using a potato and different concentrations of sucrose solution and measuring the length of the potato chips to discover their osmotic potential Osmosis is defined as "The passage of water from a region of high water concentration through a partially-permeable membrane to a region of low water concentration." (www.purchon.com.) This definition can be interpreted as the instant of where the water molecules travel from a high concentration of water to a low concentration through a semi-permeable membrane, Because it is only a semi-permeable membrane it is made up of thin layers of cells that allow molecules smaller in size i.e. oxygen or carbon dioxide through however prevent larger molecules like glucose or proteins seeping through. The osmosis process contains three different types of solution. * Isotonic Solution This is achieved when both sides have the same concentration. At this point they have reached what is called a dynamic equilibrium * Hypertonic Solution This is when there is a higher concentration of the solute on one side compared to the other where there would be a lower concentration of the solute * Hypotonic Solution This is the opposite of a hypertonic solution; here there would be a lower concentration of the solute compared to the other side. Effects of osmosis on plant cells (bbc.co.uk) Plant cells have a strong cell wall to support themselves, so when they take up water in osmosis it is the cell wall that stops the cell from bursting. ...read more.

Middle

chips in for a longer period of time if I wish to get sufficient below is the same experiment but for 30 Minutes. Distilled water Sucrose solution 30% Size of potato before experiment (cm) 2.5 2.5 Size of potato after experiment (cm) 2.61 2.30 Change in size (cm) +0.11 -0.2 This pilot I changed only the time I left the chips in for. Instead of leaving the chips in for 10 I left them in for 30 minutes. I have decided that I will leave the chips in for 30 minutes to allow for sufficient water movement and to gain a more reliable set of results Safety Precautions * Make sure all hair is tied back * Maintain a clean and tidy working environment * Wash hands before and after experiment * Stand at all times Equipment list Potato- Same size and same shape Sucrose solution 5 Test tubes Test tube rack 2 25cm measuring cylinder Scalpel Timer Cork borer Vernier Callipers Distilled water Method 1) Insure Equipment is all present and correct 2) Cut 15 potato chips using a scalpel assuring that they are all the same length, size and weight (2.63cm) 3) With a measuring cylinder measure out Sucrose solutions needed 4) Place three potatoes in each test tube with the varying solutions and start timer 5) After every 5mins for 30mins take out the chips and measure with Vernier Callipers 6) Record results in table Fair Test For the results to be credible this experiment must be a fair test. ...read more.

Conclusion

However we did record a small number of anomalous results. Repeating the experiment more times would have produced more accurate results but due to time constraints this was not possible. Limitations and Improvements There are a Varity of reasons for the anomalous results one of which being that not all of the chips were 2.60cm they could have in theory been out by 0.01. This could have been improved by measuring the chips to a greater degree of accuracy. In each test tube there were three potato chips this could have affected the results because the concentration of glucose would change. Putting one chip in each test tube may have improved reliability. Human error could be at fault as mistakes may have been made when using the Vernier callipers. Firstly when measuring the initial size of the chip then measuring the final size of the potato once osmosis had taken place. Also the solutions that were being used were made up using water and pure sucrose when constructing the mixture it may not have been entirely accurate leading to unreliable results. Variables like temperature were not able to be controlled; some test tubes may have been left in sunlight whereas others may have been left in shade. Instead of measuring the size of the potato chip nest time we could record the mass of the chip this would cut down on human error. To further the investigation we could experiment with different types of potato recording which ones have the most net movement of water. Furthermore we could more concentration intervals doing this would allow for further analysis of results ...read more.

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