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Osmosis Experiment. This experiment is to consider how salinity influences osmosis in potato cells.

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Introduction

How different concentrations of sodium chloride influence osmosis in potato cells 03/11/2010 Table of Contents 1.1 Defining the problem 3 Research Question 3 Hypothesis 3 Background Information 3 Osmosis 3 Effect of Salinity on Potato Cells 3 Salinity Concentrations 4 TABLE 1: Practical Investigations Variables 4 TABLE 2: Replicate Options 5 1.2 Controlling Variables 6 Control Experiment 6 TABLE 3: Control Treatment of Variables 6 1.3 Experimental Method 7 TABLE 4: Materials 7 Method 7 DIAGRAM 1: Experimental Set Up 1 (No time limit) 8 DIAGRAM 2: Experimental Set Up 2 (Short time limit) 8 2.1 Recording Raw Data 9 2.1.1: TABLE 5 Quantitative Data 9 2.1.2: TABLE 6 Qualitative Data 10 2.2 Processing Raw Data 10 2.2.1 TABLE 7: Mass of potato cubes after osmosis 10 2.2.2 TABLE 8: Sample Calculation 11 2.3 Presenting Processed Data 11 2.3.1 TABLE 9: Results Table 11 2.3.2 GRAPH 1: Results Graph 12 3.1 Conclusion 13 3.2 Evaluating Procedures 13 3.2.1 Reliability 13 3.2.2 Limitations/ weaknesses/ errors in laboratory investigations 13 Time as the main issue 13 Measuring Scales 13 3.3 Improvements 14 1. Design 1.1 Defining the problem Research Question Have you ever accidentally cooked a solanum tuberosum (potato) in high sodium chloride (salt) concentrated water? What was the result? This experiment is to consider how salinity influences osmosis in potato cells. By changing the concentration of salt (0%, 0.2%, 0.4%, 0.6%, 0.8%) within the water, the weight of the potato cube will be lighter or heavier than its original weight because water will exit or enter the cell due to osmosis. Hypothesis The hypothesis for this experiment is that as the concentration of the salt increases, the mass of the potato decreases. According to the osmosis theory, when a plant cell is placed in a high concentrated salt solution, the mass will decrease because the potato is less concentrated than the salt solution and the water will move through the membrane of the cell and into the stronger solution. ...read more.

Middle

Each test tube should be able to hold a 1cm x 1cm x 1cm potato cube and 15ml of salt concentrated solution. Place This experiment should be conducted indoors to reduce the number of uncontrolled variables. If this experiment was conducted outdoors, it would increase the risk of bugs, weather danger and the temperature change would be wider. As a consequence the results would not be as accurate as conducting the experiment indoors. Type of potato The best method to control the type of the potato is to use just one potato. Size of potato cubes Try and equally cut 1cm x 1cm x 1cm potato cubes. This is a good size because the glass of the test tube won't hit the potato cube meaning that the salt water will fully cover the whole potato cube. 1.3 Experimental Method TABLE 4: Materials This table below shows the apparatuses needed to perform the experiment. Apparatus Quantity Absorbent paper 5 Measuring scale +0.001g 1 250ml beaker 1 Whole potato 1 Corer 1 Scalpel 1 Tile 1 50ml measuring cylinder 5 Test tube holder 1 Fat test tubes (holds at least 25ml) 25 (if there is no time limit), 5 (if there is a time limit) Forceps 1 300mm ruler 1 0.2%,0.4%, 0.6%,0.8% salt water 75ml each (75ml x 4 = 300ml) if there is no time limit 15ml each (15ml x 4 = 60ml) if there is a short time limit Diluted water 75ml Method 1. Collect the all the apparatuses to start the experiment. Gather everything on the list above. 2. Once all the apparatuses are ready for use, stab the corer into the potato several times. 3. Cut the potato strands into measurements of 1cm by 1cm using a scalpel 4. After 25 potato cubes have been cut, measure each one of them using a measuring scale so that they are all the same weight. ...read more.

Conclusion

Measuring Scales One major problem with the measuring scale was the time. These types of scales take some time to get an accurate reading, but if there is a time set for the experiment, and there wasn't much time left before the end of the set time, the experimenter may fall into the trap of leaving the mass of the object on for just a second or so, and recording the data. This is an easy error but it is also a major one because the mass could be many hundred milligrams off the experimental mass. Another negative factor about the measuring scale is the sensitivity. With the measuring scales that were used for the experiment, they were extremely sensitive. Whenever pressure is applied around a 30cm radius (approximate estimation) from the measuring scale, the measurement on the scale changes, thus making the experiment take longer and also making the results inaccurate. The experimenter may be left with no choice but to record false data if there is time set because waiting for the correct recording may take many ten seconds. The investigations recorded closer to the time limit (0.6% & 0.8%) were the only investigations that didn't agree with the hypothesis. Perhaps the experimenter fell into the measuring scale time trap, and recorded faulty results. 3.3 Improvements There is only one main improvement that will fix all or most errors. That is time. If there was no time limit, there would not have been any pressure nor fallen for the measuring scale trap and the experimenter may have cut the potato cubes with care. 5. Reference List Purchon, Nigel, 2000, An account of osmosis for GCSE biology students, viewed 05/10/10, <http://www.purchon.com/biology/osmosis.htm> Terry Brown, 1999, Membrane- Osmosis,TVDSB, viewed 05/10/10 2010<http://www.tvdsb.on.ca/westmin/science/sbi3a1/cells/osmosis.htm> The Smartacus Corporation 2005, Osmosis in a Plant Cell, viewed 05/10/10 <http://www.college-cram.com/study/biology/cell-membranes/osmosis-in-plants-a93047> John McCandless, 1998, Diffusion, Osmosis and Cell Membrane, University of Arizona -Department of Biochemistry, viewed 05/10/10 <http://biology.arizona.edu/sciconn/lessons/mccandless/reading.html> ?? ?? ?? ?? ...read more.

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