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Osmosis
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Osmosis in Potato Cells Aim In this investigation my aim is to explore the effect of varying the concentration of a certain sugar solution on the amount of osmotic movement there is between the solution and the size of the potato piece used. Hypothesis Osmosis is defined as the passage of water molecules moving from a region of low concentrated solution into a region of highly concentrated solution. This course of action takes part through a partially permeable membrane, such as a cell membrane that lets minor molecules such as water through but does not allow bigger molecules to pass through. This type of diffusion and is a passive process, which does not require any input of energy. In this case, the tiny holes in the membrane of the potatoes will allow the water molecules to pass through in and out of the solution and potato, depending on the concentration gradient of the two substances. Water molecules voyage in both directions but there is a net movement of molecules from a higher to lower water potential. So, when the water concentration is inferior in the tissue, the water will go inside the tissue of the potato, and the potato will gain weight. And if there is very little difference in the water concentrations, there shouldn’t be a colossal change in weight and if there is a higher concentration of water in the potato, the water will go out of the potato. The molecules will continue to diffuse until the area in which the molecules are found reaches a position of equilibrium, meaning that the molecules are aimlessly dispersed throughout an object, with no area having a higher or lower concentration than any other. Water can move from A to B and B to A. though, more water passes from A to B because water is more expected to hit the membrane since there is higher water potential in A. Plan I apparatus I need will be: o Measuring Cylinder – to measure the solutions o Distilled Water – part of the experiment o Sucrose Solution – part of the experiment o Potato – part of the experiment o Tissue Paper – to dry the potato chips o Electronic Balance – to weigh the potato chips o Core Borer – to cut out potato pieces o Test Tubes – for the experiment to take place in o Beakers – to make the different concentrations of solution The apparatus will be set us as shown below: I will make sure that I precisely measure the mass of the potato pieces before and after incubation by making sure that I have dried them thoroughly by taking away all excess fluids that could influence the mass. This will be done so that I can work out which solution osmosis has taken place in the most. I will change the concentrations of the sucrose solution using a range of concentrations. I will use at least five concentrations that will be very equally spread out. The concentrations I will be using are 0%, 20%, 40%, 60%, 80% and 100% of sugar solution. Other factors involved which might affect my results. These are: o Temperature of water o Size of chip o Light o Mass of potato o Volume of solution potato is in o Type of potato o Time left in solution o Surface area of potato chip o Using the same balance to measure chip If I wish to make this a fair test, then I will have to think about these other factors. Doing the tests at one permanent temperature will control the temperature of the solution. For the principle of my experiment I am going to do all of them at room temperature.
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