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Osmosis Biology

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Introduction

Design Research question To investigate the effects of concentration of sodium chloride towards the osmosis in plant cells Variables Independent variable : Concentration of sodium chloride Dependent variable : Mass of potatoes Controlled variable : * Type of potatoes * Size of potatoes * Size of cork borer * The duration of potatoes left in test tubes * The temperature, humidity of the location of experiment * Electronic balance Prediction Based on my first speculation, I predict that the mass of the potato will decrease because water will move from a high concentration of water in the potato to a lower concentration of water in the salt solution through osmosis. I was able to predict this using my scientific knowledge. My prediction was similar to the information about osmosis on the site that I have researched below. According to http://www.purchon.com/biology/osmosis.htm, osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. In a closer scrutiny, based on the site http://www.courseworkhelp.co.uk/GCSE/Science/17.htm, when plant cells take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in diluted solutions. ...read more.

Middle

Environment/Location of experiment 5. Length of potato slices 1. Use a measuring cylinder to work out the volume of solution for each boiling tube. 2. Getting down at eye level to make sure the meniscus of the solution reaches 100ml. 3. Use of a cork borer to make sure the diameter of the potato is constant. 4. It is difficult to keep the time accurate; however I would drop each potato sample into a boiling tube for my first set of experiment promptly. Then, wait two minutes before dropping the next potato slices into the next set of boiling tubes, and do the same for my third set of boiling tubes and so on. 5. The experiment was carried out in the same environment of room temperature and location to ensure that it does not alter the results of the experiment. 6. Taping the ruler onto the cutting board so it would not slip when the potatoes are being measured. These variables are controlled to ensure accuracy and reliability to make sure facts like the volume of solution, size of potato, duration of the experiment and the location of the experiment do not alter the results of the experiment. Data Collection and Processing Raw data table Treatment of uncertainties Throughout the experiment, I've encountered a few error such as error for the equipments used. ...read more.

Conclusion

Evaluation Weakness/ Limitation How it affected my results? How I could improve it? Narrow range of salted solution used Limited amount of data Using more intervals for the solution such as 0% and other intervals to achieve equilibrium Not repeating the experiment enough times Standard deviation might not be entirely reliable Carry out the experiment more times Inaccuracy in measuring the salt solution Inaccurate measurements which likely will alter results Using a measuring cylinder with smaller measurements Intervals of putting potato slices into the solution Some potatoes might be left in the test tubes longer than the others. This can alter the results. Get help from friends to drop the potato slices into the test tubes all at once Line of best fit is very far from the points in the graph This shows inaccuracy of the results Using more data and more intervals of solution such as 2.5%.3%,3.5%,4.5%,5% and so on to achieve an accurate line of bestfit Carrying out the experiment with 100ml of solution in the test tubes This promotes inaccuracy as the intervals are large To be more accurate 50 ml test tubes should be used Drying each potato one by one The time intervals of drying the potato causes the results to vary Help from friends to dry the potato slices all at once ...read more.

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