A Level Coursework

Topics: Osmosis, Concentration, Water Pages: 3 (1218 words) Published: March 18, 2013
Osmosis in Potato Cells
My results show what I predicted would happen. My prediction was that as the concentration of sucrose increased the amount of water moving in or out of the potato would change. A low concentration of sucrose solution would make the potato increase in length and mass (become turgid). A high concentration of sucrose solution would make the potato shrink (plasmolysed) We can see this occurred, as at 0.1mol of sucrose solution the potato’s size increased by an average % change in mass of +11.78%, whereas at 0.7mol the potato shrank by an average change of mass of -50.93%. Clearly showing that my prediction was correct and that osmosis occurred.

The aim of this investigation was to discover the effect that water concentration had on the mass of potato tissue, and to investigate the movement of osmosis through potato tissue, osmosis being the passage of water molecules from a weaker solution to a stronger solution, though a partially permeable membrane. In this case, the membrane of the potatoes allowed the water molecules to pass through in and out of the solution and the potato, depending on the concentration gradient of the two substances. The water potential of a solution is a measure of whether it is likely to lose or gain water molecules from another solution. A dilute solution, with its high proportion of free water molecules, will have a higher water potential than a concentrated solution, because water flows from the dilute to the concentrated solution (from a high to low water potential). Pure water (Distilled Water) has the highest possible water potential because water molecules will flow from pure water to any other aqueous solution, no matter how dilute. When two such solutions (one strong, one weak) are separated by a semi-permeable membrane, the water will move from the side with more water to the side with less until both sides are equal (equilibrium). In this experiment the water potentials of both the...
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