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Osmosis. In this investigation we are going to be monitoring the sucrose sugar solution concentration change on the mass of a potato.

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Introduction

Coursework - Osmosis In this investigation we are going to be monitoring the sucrose sugar solution concentration change on the mass of a potato. We are basing our investigation on the process of osmosis. This is the net movement of water molecules from a region of their higher concentration to a region of their lower concentration, through a partially permeable membrane: Water molecules move from where there is more water, to where there is less, as long as the membrane separating each is partially permeable. The cell membrane, which is a type of lipid, allows water to pass through it. Therefore, many water molecules are moving in each direction. When it is found out that a change in mass has happened in either substance it is because there has been a large movement of water molecules in one direction to make the concentration equal in both substances. This could be explained with the collision theory and looking at the diagram above. When there is an equal concentration of water on each side then the water molecules will pass through each side of the membrane at the same rate, so that one side is replacing what has gone out of the other side. This will maintain an equal balance of water molecules on each side. However, with our experiment and shown in the diagram above, one side (left) has a lower concentration of water molecules as it has glucose molecules too, when the other side has the equivalent but just with water molecules. Therefore it has a higher concentration. Because the membrane only allows water molecules to pass through it, the glucose molecules get stuck preventing water molecules to get through and therefore disturbing the normal rate of water movement. Now that is happening, less water molecules on the left are passing to the right because they have less space to transfer molecules. However, on the right side the same rate of movement is going on and so the water molecules on the right ...read more.

Middle

(The possible outcome variables are highlighted, standing out from the rest of the text) Out of all these possible outcomes, I will still be looking at the percentage change in mass of the potato chip, as this will be the most accurate and precise result. This is because the change in volume and concentration of sugar will be too difficult to measure. The change in the length of the potato Chip will only be very small and very difficult to determine. The change of mass of the potato chip will not be very precise, as I am not controlling the starting mass. After discussing in detail above how osmosis happens and looking at the factors that determine the rate of osmosis, I have come to the prediction that the larger the difference in concentration between the two substances, the faster the rate of osmosis or the more the osmosis will take place. The bigger the concentration, the more osmosis is needed to lose water or absorb water and make both substances equal. If the concentration of glucose in the potato chip is higher then water molecules will pass from the solution into the potato chip, therefore, increasing the mass of the potato chip and making it grow in size. However, if there is a higher concentration of glucose in the solution, then water molecules will pass from the potato into the solution, therefore, decreasing the mass of the potato and making it shrink in size. So therefore, I definitely believe that a change in the concentration of the solution will have some kind of effect on the mass of the potato chip, due to osmosis. Knowing my prediction I am now going to write out a suitable method for my experiment and then carry out this method as accurately as possible: * Firstly I will prepare the solutions by putting them in test tubes with the concentrations of 0%-25% sugar solution. ...read more.

Conclusion

When 10% is added the potato loses 0.12 grams. From then on the changes get bigger because we are then just adding to the concentration and making the difference between the two substances even bigger. This means that osmosis has to work at a faster rate or osmosis will have to take place a lot more and therefore, there will be a bigger loss in weight. This is shown as we get a decrease of 0.27 grams with 15%, followed by a decrease of 0.38 grams with 20% concentration and finally the biggest being a 0.41 gram decrease with 25% concentration added in. The concentration of sugar solution and the average percentage increase are inversely proportional. This means that as the concentration of sugar solution goes up, the average percentage increase goes down. You can see this clearly in my graph: Looking at my graph I can clearly say that it justifies my prediction about osmosis in our experiment. Like I stated before, it follows a negative correlation and this is what I said in my prediction too; In my prediction I said that the larger the difference in concentration between the two substances, the faster the rate of osmosis or the more the osmosis will take place. This is true with the experiment because when the concentrations got bigger, this added a bigger difference between the two substances and therefore there was a bigger change in mass to transfer the difference in water to the other substance. On the graph you can see that the bigger the concentration, the bigger the decrease in mass, as it is quite proportionally going down in a negative correlation. Also in my graph you can clearly see the difference between 0% concentration and a 25% concentration sugar solution, when added to the distilled water. When it has 0% there is a 0.15-gram increase, but when there is 25% sugar concentration in the solution there is a 0.41-gram decrease. This means that there is a 0.56-gram difference in the increase and decrease put together, which shows the difference between the two. Luca Capobasso ...read more.

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