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  • Level: GCSE
  • Subject: Science
  • Essay length: 4566 words

Aim: To find out the effect of altering the concentration of sugar solution on osmosis in potato chips.

Extracts from this essay...

Introduction

Osmosis Investigation Aim: To find out the effect of altering the concentration of sugar solution on osmosis in potato chips. Introduction Osmosis is an integral part of the OCR 21st Century Science course and comes up in Module B4 Homeostasis. This unit of work was the inspiration behind my choice of coursework. This area provides me with the opportunity to see science in action. The investigation chosen is one that can be safely carried out and the results can be readily observed and recorded without expensive lab equipment. Osmosis is the diffusion of water across a partially permeable membrane from a region of high water concentration to a region of lower water concentration. This process takes place until equilibrium is established. Osmosis is a passive process. This means it happens naturally as all particles have some kinetic energy. Factors that affect Osmosis There are many factors that affect osmosis which are listed below: * Temperature * Surface Area * Concentration * The amount of water on each side of the membrane The factor that I am looking at in my experiment is the concentration of the sugar solution in the reaction. This particular factor was chosen as it is relatively easy to prepare different concentrations of solutions and it is without the need of expensive lab equipment. The method selected for carrying out this experiment is one that involves extensive use of laboratory skills and is one in which concentrations can readily altered and their effect measured without the use of complicated and expensive scientific equipment. I am able to carry out this investigation by myself at home. How does concentration affect the amount of Osmosis? Concentration is a measure of the number of particles of a particular solute in a given volume of solvent. A dilute solution is likely to contain fewer molecules of the solute and more water molecules. A concentrated solution is likely to contain more solute molecules and fewer water molecules in the same total volume of solution.

Middle

The final mass will be recorded and then I would work out the change in mass and a % change in mass. The test tubes will need to be rinsed out with distilled water and dried before being reused. After this, I will repeat the procedure with different concentrations of sugar solutions. In the main investigation I will collect twelve pieces of data. The experiment will be carried out at six different concentrations of sugar solution and each experiment will be repeated to get an average result. This will increase the reliability of the results. The range of concentrations as mentioned before will be; 0%, 20%, 40%, 60%, 80% and 100% sugar solutions. The data will be as accurate as possible by ensuring a fair test is carried out. This will be done by ensuring that the following actions are taken; * The concentration of the sugar solution will be kept constant - this will be done by making a sample stock of sugar solution of a known concentration which will then be used in all the experiments. * The volume of the sugar solution will need to be kept constant - this will be done by making use of the measuring cylinder so the sugar solution is accurately measured out and poured into the test tube for each experiment. * The concentration of the potato chips will need to be kept constant - this will be done by using similar types of potato chips, both in terms of brand of potato, size and dimensions. * The Temperature of the solution mixture will also be kept constant. This will be done by carrying out the experiment in the same environment and carried out at the same time - I will measure the temperature of the reaction mixture using a thermometer to ensure it stays the same. * The Dimensions/cross-sectional area of potato chips will also be kept constant by using potato chips of same length and width and using the same size borer to make all the potato chips.

Conclusion

Firstly a larger range of concentrations could have been tested with smaller increments i.e. concentration going up in increments of 10% increase rather than the 20% increase in concentration. To increase the reliability the experiment could have been done with more repeats rather than just testing each concentration three times we could have repeated each one five times to obtain a more reliable average. Arguably the most significant weakness in the whole method was the use of the human eye to detect when the cross was completely obscured. This is not a subjective way of doing things and human error creeps in. To overcome this shortfall I suggest making use of ICT. I think that a data-logger can be connected to a light sensor and this would record the change in light intensity as the reaction proceeds and produce real time graphs. This method then removes the human error and is objective. A further advantage is that real time graphs are produced and this means if there is an error or an anomalous result it can be detected straight away discarded and the experiment carried out again which further improves the accuracy and reliability of the results. Below is a diagram which shows how the data-logger could be connected in this experiment. Prediction I predict that in a dilute sugar solution, the potato chip will gain mass. This is because, there will be more water particles around the outside of the potato chip so the water particles will be moving in, thus expanding the potato chip. However, in a more concentrated sugar solution the potato chip will shrink. This is because there will be less water particles around the outside of the potato chip and so the water particles will be moving out, hence shrinking the potato chip. Overall, as the concentration increases, I will expect the mass of the potato chip to decrease. Glossary (1) Education & Reference Questions and Answers Web http://www.eduqna.com (2)

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