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The Chips Problem

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Introduction

Rebecca Thomas The Chips Problem Aim: To investigate which salt water concentration causes the potato chips to neither swell nor shrink. Explanation of Aim: Osmosis is the movement of water from an area of high water potential to an area of low water potential, across a partially permeable membrane, until equilibrium is achieved. Equilibrium is the movement of water by osmosis, entering and leaving the cells at a constant rate. Osmosis: Partially Permeable Membrane Water Salt Solution High Water Potential Low Water Potential Water Particle Salt Particle If the potato chips are placed in a solution containing a higher concentration of free water particles outside the chip than there are inside the chip, then the water enters the chip by osmosis, causing it to swell and therefore become turgid. Turgidity is caused by water entering the cells at a faster rate than it leaves. This excess water in the vacuole causes a high internal pressure, instigating the chip to be well supported and strong, and to therefore grow in length. A Turgid cell: Cell Wall Cell Membrane Vacuole Nucleus High Water Potential When the potato chips are placed in a solution containing fewer free water particles outside the cells than in, water leaves the chips by osmosis. ...read more.

Middle

free water particles outside of the chip, which would then cause there to be a possible higher concentration of free water particles inside the chip, so water would move out by osmosis, when it should have moved in. The potatoes in these solutions would become flaccid and lose mass. * Shake each test tube so that the solutions are well mixed and all of the particles are able to surround the chip equally. * Once the test tubes have been shaken, start the stopwatch. * Allow the chips to remain in the solutions for twenty-four hours, as osmosis is slow because it does not require energy. * Replications of the concentrations will enable you to identify any anomalous results, and to then discard them. They also allow you to calculate a mean result, which is more reliable than one result. * Record your results in a results table and produce a graph that shows the percentage change in mass against the concentrations. Apparatus: Cork borer: 6mm diameter 18 Test tubes Blotting paper Top-pan balance Test tube racks Ruler Scalpel Stopwatch Two syringes Potato Fireproof mat Cling film Sellotape Forceps 10% salt solution Distilled water Two beakers Safety: Care should be taken when cutting the potato cylinders with a scalpel. ...read more.

Conclusion

To improve the experiment, I could improve the overall accuracy of how it was executed. For instance, I could ensure that any preparations are completed for the same lengths of time, for example, the cutting and weighing times. To improve reliability, I could replicate five times instead of three, which would mean that I could discard any anomalous results and calculate a more reliable mean result, which is better than just one result. For further work which would provide additional evidence to support my conclusion, I could investigate more accurate concentrations, such as 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8 and 6% salt water concentrations, as I know that the most suitable concentration is around 5%. To extend my enquiry, I could investigate other variables that might affect the rate of osmosis, and therefore, the change in mass of the potato chips. For example, the surface area of the chips might have an affect, because the larger the surface area of the chip in proportion to its volume, the faster the rate of osmosis, as there would be a greater region for the water to enter or leave the potato chip cells, at a much faster rate. Also, we could investigate how the temperature affects the rate of osmosis. Perhaps if it is warmer, then osmosis will occur at a faster rate because the enzymes will have energy to move quickly. ...read more.

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