Alexandra K. FeketeGroup 4January 2018Aim – The aim of this experiment was to investigate how different concentration of sucrose affect on the rate of osmosis on cubes of potatoes This was done by using potato cubes cut out for the exactly same size 2 cm lenght 1cm width and 1cm height. And applying them into beakers filled with different concentration of sucrose solution . ”0.
0 % 0.2% 0.4% 0.6% 0.8% and finnaly in 1.
0% . Then the mass of potato cubes needed to be recorded after . The amount of time were used to soak the potato cubes were 40 minutes .Hypothesis- Results were predicted that if the potato cubes were placed into sucrose concentration where the water potential is highert than the water potential of the potato itself than it would cause the mass of potato to increase and if they had similar water potential there will be no change in the mass , and lastly is the water potential of sucrose is less than the water potential of the potato means the mass of potato will decrease Background- Osmosis is the movement of water molecules .
Water molecules move from a higher water poential to a lower water potential through a semi permeable membrane . There is few factors that effect the rate of osmosis including the size of particle and temperature however the factor That is investigated today is the concentration of the sucrose As the concentration of sucrose increses the mass of potato also increases because it has been placed in a hypertonic solution which means that it has a higher amount of particles dissolved in the solution .Variables-Independent variables – The concentration of Sucrose solution in which potato cubes were placed in . 0.0%, 0.2% 0.
4% 0.6% 0.8% 1.0% Dependent variables- `:The change in mass of the potato cubes before and after the experimentRatios: To be able to balance different Surface-area-to-volume ratio to limit effect on the rate of osmosis the sizes it must first should be measured using a ruler maintain the same diameter for each cuboid of potatoType of tissue – The type of tissue has a very big effect on the rate of osmosis because the amount of glucose in each type of tissue is different , This can be controlled by using only one type of tissue which means is using the same potato to make the 6 cuboids.Materials used 1 Large Potato (cut into 6 cuboids)White TileRulerBeakers 6xElectric scaleSucrose (0.0 , 0.
2, 0.4 ,0.6 , 0.8 , 1.0 )Filter paper 6xKnifestopwatch/timerProcedureAt the beggining of the experiment lab coats were put on .Risk assesment was filled out .6x filter paper was labeled ( concentration of sucrose, weight of the potato before and after )Potato was peeled using the knife Potato skin(waste) was placed in a plastic container labeled as waste6 cuboids were cut out using a ruler and the same potato .
Each cuboid was measured to be 2cm x 1cm x 1cm .Anymore waste was disposed The electric weighing scale was plugged in The weighing scale then was turned on The scale was set to gramsNext the labeled filter paper was placed on the scale Scale was set to 0 again before a piece of potato were placed on it to measure the mass This was repeated 6x times for each cuboidThen all cuboids were placed in the sucrose , 1 cuboid in each beaker The cuboids were left to soak for 40 minutes The cuboids then were removed one by one and placed on the scale on a filter paper ( excess water to be shaken off) the tear button MUST be pressed before placing the potato on the filter paper .The mass was recorded and this step was repeated 6x for each cuboid . All the waist was placed in the plastic container and equipments were placed back inside the red tray . The scale was unplugged and the plug was switched off for safety matters Observations The poatato cuboids were floating in the 0.6, 0.8.
1.0 sucrose solution . However in 0.0 ,0.2 and 0.4 the cuboids were sinking , at the bottom of the Data collection Concentration of sucroseInitial mass of potato cuboidFinal mass of potato cuboid% change of mass 0.
14g-5.6%ConclusionThe table of results above show the effect of osmotic activity inside the potato pieces by the water molecules moving throughout a semipermeable membrane which exists within the concentration gradient. The molecules move into an area of lower concentration which in this case is the sucrose solution because osmosis takes place from a high water concentration to a low water concentration area . The more osmotic activity which took place resulted in the potato pieces decreasing their weight. The table shows that the pieces of potato which were placed in a 0.
2 concentration or less increased in weight however those which were placed in a 0.4 molar concentration or higher decreased in weight.As stated in the hypothesis result was predicted that there would be a decrease in weight As the potato cell was surrounded by a more concentrated solution this resulted in there being a lower water concentration within the potato cell which meant osmosis took place making it hypertonic. As predicted, results were correct the potato pieces which were more water concentrated have weighed more compared to the other potato pieces which were placed in a more sucrose concentrated solution. EvaluationOverall the experiment went very well as there were no major mistakes were made during the experiment. The method which was used to conduct the experiment was very suitable .
It wasn’t hard to understand at all and it was not time consuming , it was very simple to carry out. Furthermore it was also a very good method to use because it helped to achieve reliable and accurate results in order to draw up an accurate conclusion. However if the experiment could be repeated there would be couple of things that could be done differently. When carrying out the experiment a range of 0, 0.2, 0.4, 0.6, 0.8 and 1 molar solution was used to see the effect of osmosis in the potato cuboids.
In the future more varied range of the concentration of the sucrose solution would be better in order to achieve a more varying range of results i.e. 0, 0.1, 0.2, 0.3 and further. There was an abnormal result as shown on the results graph and table as the 1.
0 molar solution was much more further away from the line of best fit. This is may have been due to the fact that the potato piece had a little bit more water potential compared to each other potato piece therefore this resulted the potato to decrease in mass only a little bit i.e. it went from 4.39g decrease in mass in the 1 molar to 4.14g (-5.6%)decrease in mass in the 0.4 molar.
As a result in carrying out any future experiments each potato piece should be soaked the same amount of time and method. However the potato pieces should have left in the solution for a longer length of time. because they were only in the beakers for 40 minutes. consider Would strongly reccomned changing the time to 60 minutes at least as there would be a more noticeable range of results therefore better conclusions could be written up . Furthermore repeating the test 3 times instead of 1 would also give a better and more accurate conclusion and results. water potential