Biology Biology 2.1 Making 2.1 Making

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What was the experiment about?Osmosis. The effects of osmosis on potato chips.

What were the variables (independent, dependent as well as range and how measured?The independent variable was the amount of salt in each salt solution. The salt solutions ranged from 0.0 mol L^-1 (distilled water) to 0.9 mol L^-1 and included 0.1 mol L^-1, 0.3 mol L^-1, 0.5 mol L^-1 and 0.7 mol L^-1. The dependant variable was how much water was absorbed between measurements.The dependant variable was measured by weighing each potato piece before and after it had been left to soak in a solution, then subtracting one from the other.

How did you ensure reliability and validity of data?By soaking three pieces of potato in each salt solution, then averaging the results.

What results did you get? Were they expected?I expected the solution with the least amount of salt (the distilled water) to gain the most weight, but I also expected the solution with the most amount of salt to loose the most amount of weight, and this was not true. The 0.1 mol L^-1 solution lost the most weight, and it only had a small amount of salt in it compared to the other solutions. The potato sticks left in the salt solutions were rubbery and slimy, while the potato sticks left in the distilled water were crisp and firm.

What is the science behind what happened? Give detailsOsmosis works by sending water from areas of high concentration (hypotonic) to areas of low concentration (hypertonic) to make them have an equilibrium (equal water content, or isotonic solution).

What is the science behind what happened? Give detailsWhen the potato sticks were left to absorb the salt solutions, they had a higher concentration of water than their surrounding environment. The water from the hypotonic environment (the potato sticks) was sent to the hypertonic environment (the salt solution).When the water left the potato cells they became flaccid, the cell membrane collapsed and made the potato stick look and feel rubbery and slimy.The potato sticks left in the distilled water were firm and crisp because the sticks themselves were the hypertonic environment, and therefore water was sent to the cells. The pressure caused by the increase of water to each cell makes the cell turgid, and the potato stick itself looks firm.

What went wrong?Some of the potato sticks were squashed into the small vials and perhaps couldn’t get as much water as some of the other sticks.

What improvements do you think you could make to this experiment?Bigger vials, smaller potato sticks or a greater volume of liquid to completely cover every stick would have worked better.