Graph 1 Lab
Data Analysis:
Graph 1 indicates the relationship between the dependent and the independent variable to be; as the concentration of sodium bicarbonate in the solution submerging the leaf discs is increased, the average rate of photosynthesis of the leaf discs increased in a linear trend. As it is the sodium bicarbonate which decomposes into carbon dioxide necessary for photosynthesis, it is reasonable to consider from Graph 1 that as carbon dioxide concentration of the solution increases, the rate of photosynthesis will also increase in a linear trend. Carbon dioxide concentration is shown to be directly proportional to rate of photosynthesis ([CO2] ∝ rate of photosynthesis). The line of best fit in Graph 1 illustrates that at 1% sodium hydroxide …show more content…
concentration the rate of photosynthesis would be approximately 0.20 per minute, the line of best fit increases at a constant rate and at 6% sodium bicarbonate concentration the rate of photosynthesis would have been approximately 0.70 per minute. This data indicates that the rate of photosynthesis increases as the sodium bicarbonate concentration and therefore the carbon dioxide concentration is increased.
The average rate of photosynthesis for each increment is credible as the relationship between rate of photosynthesis and carbon dioxide concentration is as theory predicts it should be. Theory suggests that if higher percentages of carbon dioxide were introduced into the solution submerging the leaf discs, the rate of photosynthesis will eventually plateau and stop increasing due to limiting factors such as x. The line of best fit suggests that if a plateau was to occur, it would occur at a concentration of more than 8%, as the relationship between rate of photosynthesis and sodium bicarbonate solution concentration seems linear up to the 8% increment.
Theory:
A solution of sodium bicarbonate (NaHCO3) has been used as a means to release carbon dioxide (CO2) for the production of oxygen (O2) through the process of photosynthesis. The carbon dioxide is produced from the sodium bicarbonate through a decomposition reaction in which a temperature of approximately 80 oC causes sodium bicarbonate molecules to break down into sodium carbonate (Na2CO3), water (H2O) and carbon dioxide (CO2) (Helmenstine, 2017);
2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(l)
The carbon dioxide produced from the sodium bicarbonate decomposition reaction is now able to be used as a product for photosynthesis in the chloroplasts of the leaf discs. Under the conditions of light (from the projector) and chlorophyll (in the chloroplasts of the leaf discs), the photosynthesis reaction can now take place as the water in the sodium bicarbonate solution reacts with the carbon dioxide to produce glucose, and oxygen;
6 CO2(g) + 6 H2O(l) → C6H12O6(s) + 6 O2(g)
Th oxygen produced will rise to the top of the solution as it is less dense than the sodium bicarbonate solution and if enough oxygen gas accumulates inside or underneath a leaf disc, the force of the oxygen rising will overcome the force of gravity and the leaf disc will also rise to the surface. For this practical, the time will be recorded when the leaf disc comes into contact with the surface as it may not be able to break through due to surface tension.
The leaf being used in the practical is the Northern Black Wattle (Acacia auriculiformus), it has an optimum temperature of approximately 25-35oC (Trivedi, 1992), the leaves do not have hair to potentially trap oxygen, pH of the tree ranges from 3.0-9.5 (Penh, 2008)
Errors:
While punching small leaf discs out of the black wattle leaves, it was noticed that while all leaf discs had the same radius and cross-sectional surface area, the thickness of each leaf disc varied. The thickness of each disk was different because they were punched out of different leaves and out of different places on the same leaf, not all places on a leaf have the same thickness. This change in thickness caused the mass of each leaf disc to vary and hence how much oxygen was required to be produced in order to lift the leaf disc to the surface of the sodium bicarbonate solution. An increase or decrease in the oxygen produced by the discs would vary the time taken for them to reach the surface of the sodium bicarbonate solution because the number of oxygen molecules produced through photosynthesis directly affects the force pushing the leaf discs to the surface of the sodium bicarbonate solution. A thicker leaf disc will require more oxygen to be produced for it to reach the surface and will therefore take longer to reach the surface which will decrease the calculated rate of photosynthesis while a thinner leaf in comparison will require less oxygen and will reach the surface of the sodium bicarbonate solution faster which will increase the calculated rate of photosynthesis. This error varies the rate of photosynthesis calculated for the leaf discs and this variance is shown in Table 1 under the ‘Percentage Error’ column. The percentage range is 0% error for 0% sodium bicarbonate solution concentration, 142% error for 2.5%, 104% error for 3%, 39.1% error for 4%, 57.3% error for 5% and 135% error for 8%. The percentage range for all trials is shown to be greatly more than the 10% acceptable percentage error. This unacceptable percentage range indicates imprecision in the calculated rate of photosynthesis and clarifies the scatter along the line of best fit drawn in Graph 1. This is a random error as its effect on the calculated rate of photosynthesis is inconsistent, therefore causing the rate of photosynthesis calculated to be imprecise and lowers reliability in data collected.
It was noticed while waiting for the leaf discs to rise to the surface of the sodium bicarbonate solution that not all air bubbles being ejected from the leaves due to photosynthesis were accumulating underneath the leaf discs.
A variable portion of the oxygen produced from each leaf disc was floating to the surface instead of staying attached to the leaf disc it was produced from. If the oxygen produced via photosynthesis is lost in the sodium bicarbonate solution, it will not be contributing to the force pushing the leaf disc to the surface of the sodium bicarbonate solution and therefore the time that the leaf discs take to reach the surface of the solution will increase. As all leaf discs were cut out using the same hole punch and therefore have the same cross section area and are orientated at the same direction to the light source, all leaf disks should have lost approximately an equal volume of oxygen from this error. This increased time for the leaf discs to ride to the surface of the sodium bicarbonate solution decreased the calculated rate of photosynthesis for all trials by an equal amount as the leaf discs will lose approximately the same amount of oxygen in each trial. This error will skew the calculated rate of photosynthesis to increase less than it should as the sodium bicarbonate concentration of the solution is increased. The effect of this error on the rate of photosynthesis calculated can be seen in Graph 1 as the line of best fit is slightly lower than the origin and is approximately -0.005 min-1 when the sodium bicarbonate concentration of the solution is 0%, the rate of photosynthesis should be 0min-1 when there is no sodium bicarbonate in the solution as there will be no carbon dioxide for photosynthesis to occur. This is a systematic error as it affects the accuracy of the rate of photosynthesis and decreases it for each
trial.
After the leaf discs had been placed in the sodium bicarbonate solution, some of them came to rest slightly overlapping another leaf disc rather than sitting right at the bottom of the 100ml beaker
Improvements:
The mass of each individual leaf discs should be weighed on a set of electronic scales before they are submerged in the sodium bicarbonate solution. Weighing the leaf disks will ensure that all leaf discs will have an equal mass and therefore have to overcome an equal force in order to reach the surface of the sodium bicarbonate solution. If the leaf discs are weighed before they are placed in the sodium bicarbonate solution, the effects of random error will be minimized.
Evaluation of Procedures:
The method created before the experiment was able to produce a rate of photosynthesis that seemed to mimic how it should work theoretically, the relationship between rate of photosynthesis and carbon dioxide in a solution containing leaf discs was shown to be correct in Graph 1. Errors have been shown to affect the rate of photosynthesis but not by a large amount and therefore it is assumed that the reliability of the rate of photosynthesis calculated is relatively high. Although the percentage ranges shown in Table 1 indicate that there was a large amount of scatter between trials of the same increment, Graph 1 does not seem to be affected by this random error very much as the scatter around the line of best fit is not extreme. Random errors were minimized by the method as it contained concise instructions with language easily understood and often repeated but for different increments so they were always carried out in a similar way.
Conclusion:
The experimental rate of photosynthesis calculated from the time in which leaf discs rose to the surface of a sodium bicarbonate solution support the hypothesis of; If the carbon dioxide concentration of the sodium bicarbonate solution submerging the leaf discs increases, the rate of photosynthesis of the leaf discs will also increase until a plateau occurs to an extent as it is not known if the experimental rate of photosynthesis would plateau at higher carbon dioxide concentrations. The level of reliability of the experimental rate of photosynthesis is medium as Graph 1 shows little scatter of points around the line of best fit, however the percentage range for increments was incredibly high suggesting random error was present in the method. Accuracy of this experiment is high as the systematic errors were not major and the line of best fit in Graph 1 cuts the axis close to the origin.
Graph 1 indicates the relationship between the dependent and the independent variable to be; as the concentration of sodium bicarbonate in the solution submerging the leaf discs is increased, the average rate of photosynthesis of the leaf discs increased in a linear trend. As it is the sodium bicarbonate which decomposes into carbon dioxide necessary for photosynthesis, it is reasonable to consider from Graph 1 that as carbon dioxide concentration of the solution increases, the rate of photosynthesis will also increase in a linear trend. Carbon dioxide concentration is shown to be directly proportional to rate of photosynthesis ([CO2] ∝ rate of photosynthesis). The line of best fit in Graph 1 illustrates that at 1% sodium hydroxide …show more content…
concentration the rate of photosynthesis would be approximately 0.20 per minute, the line of best fit increases at a constant rate and at 6% sodium bicarbonate concentration the rate of photosynthesis would have been approximately 0.70 per minute. This data indicates that the rate of photosynthesis increases as the sodium bicarbonate concentration and therefore the carbon dioxide concentration is increased.
The average rate of photosynthesis for each increment is credible as the relationship between rate of photosynthesis and carbon dioxide concentration is as theory predicts it should be. Theory suggests that if higher percentages of carbon dioxide were introduced into the solution submerging the leaf discs, the rate of photosynthesis will eventually plateau and stop increasing due to limiting factors such as x. The line of best fit suggests that if a plateau was to occur, it would occur at a concentration of more than 8%, as the relationship between rate of photosynthesis and sodium bicarbonate solution concentration seems linear up to the 8% increment.
Theory:
A solution of sodium bicarbonate (NaHCO3) has been used as a means to release carbon dioxide (CO2) for the production of oxygen (O2) through the process of photosynthesis. The carbon dioxide is produced from the sodium bicarbonate through a decomposition reaction in which a temperature of approximately 80 oC causes sodium bicarbonate molecules to break down into sodium carbonate (Na2CO3), water (H2O) and carbon dioxide (CO2) (Helmenstine, 2017);
2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(l)
The carbon dioxide produced from the sodium bicarbonate decomposition reaction is now able to be used as a product for photosynthesis in the chloroplasts of the leaf discs. Under the conditions of light (from the projector) and chlorophyll (in the chloroplasts of the leaf discs), the photosynthesis reaction can now take place as the water in the sodium bicarbonate solution reacts with the carbon dioxide to produce glucose, and oxygen;
6 CO2(g) + 6 H2O(l) → C6H12O6(s) + 6 O2(g)
Th oxygen produced will rise to the top of the solution as it is less dense than the sodium bicarbonate solution and if enough oxygen gas accumulates inside or underneath a leaf disc, the force of the oxygen rising will overcome the force of gravity and the leaf disc will also rise to the surface. For this practical, the time will be recorded when the leaf disc comes into contact with the surface as it may not be able to break through due to surface tension.
The leaf being used in the practical is the Northern Black Wattle (Acacia auriculiformus), it has an optimum temperature of approximately 25-35oC (Trivedi, 1992), the leaves do not have hair to potentially trap oxygen, pH of the tree ranges from 3.0-9.5 (Penh, 2008)
Errors:
While punching small leaf discs out of the black wattle leaves, it was noticed that while all leaf discs had the same radius and cross-sectional surface area, the thickness of each leaf disc varied. The thickness of each disk was different because they were punched out of different leaves and out of different places on the same leaf, not all places on a leaf have the same thickness. This change in thickness caused the mass of each leaf disc to vary and hence how much oxygen was required to be produced in order to lift the leaf disc to the surface of the sodium bicarbonate solution. An increase or decrease in the oxygen produced by the discs would vary the time taken for them to reach the surface of the sodium bicarbonate solution because the number of oxygen molecules produced through photosynthesis directly affects the force pushing the leaf discs to the surface of the sodium bicarbonate solution. A thicker leaf disc will require more oxygen to be produced for it to reach the surface and will therefore take longer to reach the surface which will decrease the calculated rate of photosynthesis while a thinner leaf in comparison will require less oxygen and will reach the surface of the sodium bicarbonate solution faster which will increase the calculated rate of photosynthesis. This error varies the rate of photosynthesis calculated for the leaf discs and this variance is shown in Table 1 under the ‘Percentage Error’ column. The percentage range is 0% error for 0% sodium bicarbonate solution concentration, 142% error for 2.5%, 104% error for 3%, 39.1% error for 4%, 57.3% error for 5% and 135% error for 8%. The percentage range for all trials is shown to be greatly more than the 10% acceptable percentage error. This unacceptable percentage range indicates imprecision in the calculated rate of photosynthesis and clarifies the scatter along the line of best fit drawn in Graph 1. This is a random error as its effect on the calculated rate of photosynthesis is inconsistent, therefore causing the rate of photosynthesis calculated to be imprecise and lowers reliability in data collected.
It was noticed while waiting for the leaf discs to rise to the surface of the sodium bicarbonate solution that not all air bubbles being ejected from the leaves due to photosynthesis were accumulating underneath the leaf discs.
A variable portion of the oxygen produced from each leaf disc was floating to the surface instead of staying attached to the leaf disc it was produced from. If the oxygen produced via photosynthesis is lost in the sodium bicarbonate solution, it will not be contributing to the force pushing the leaf disc to the surface of the sodium bicarbonate solution and therefore the time that the leaf discs take to reach the surface of the solution will increase. As all leaf discs were cut out using the same hole punch and therefore have the same cross section area and are orientated at the same direction to the light source, all leaf disks should have lost approximately an equal volume of oxygen from this error. This increased time for the leaf discs to ride to the surface of the sodium bicarbonate solution decreased the calculated rate of photosynthesis for all trials by an equal amount as the leaf discs will lose approximately the same amount of oxygen in each trial. This error will skew the calculated rate of photosynthesis to increase less than it should as the sodium bicarbonate concentration of the solution is increased. The effect of this error on the rate of photosynthesis calculated can be seen in Graph 1 as the line of best fit is slightly lower than the origin and is approximately -0.005 min-1 when the sodium bicarbonate concentration of the solution is 0%, the rate of photosynthesis should be 0min-1 when there is no sodium bicarbonate in the solution as there will be no carbon dioxide for photosynthesis to occur. This is a systematic error as it affects the accuracy of the rate of photosynthesis and decreases it for each
trial.
After the leaf discs had been placed in the sodium bicarbonate solution, some of them came to rest slightly overlapping another leaf disc rather than sitting right at the bottom of the 100ml beaker
Improvements:
The mass of each individual leaf discs should be weighed on a set of electronic scales before they are submerged in the sodium bicarbonate solution. Weighing the leaf disks will ensure that all leaf discs will have an equal mass and therefore have to overcome an equal force in order to reach the surface of the sodium bicarbonate solution. If the leaf discs are weighed before they are placed in the sodium bicarbonate solution, the effects of random error will be minimized.
Evaluation of Procedures:
The method created before the experiment was able to produce a rate of photosynthesis that seemed to mimic how it should work theoretically, the relationship between rate of photosynthesis and carbon dioxide in a solution containing leaf discs was shown to be correct in Graph 1. Errors have been shown to affect the rate of photosynthesis but not by a large amount and therefore it is assumed that the reliability of the rate of photosynthesis calculated is relatively high. Although the percentage ranges shown in Table 1 indicate that there was a large amount of scatter between trials of the same increment, Graph 1 does not seem to be affected by this random error very much as the scatter around the line of best fit is not extreme. Random errors were minimized by the method as it contained concise instructions with language easily understood and often repeated but for different increments so they were always carried out in a similar way.
Conclusion:
The experimental rate of photosynthesis calculated from the time in which leaf discs rose to the surface of a sodium bicarbonate solution support the hypothesis of; If the carbon dioxide concentration of the sodium bicarbonate solution submerging the leaf discs increases, the rate of photosynthesis of the leaf discs will also increase until a plateau occurs to an extent as it is not known if the experimental rate of photosynthesis would plateau at higher carbon dioxide concentrations. The level of reliability of the experimental rate of photosynthesis is medium as Graph 1 shows little scatter of points around the line of best fit, however the percentage range for increments was incredibly high suggesting random error was present in the method. Accuracy of this experiment is high as the systematic errors were not major and the line of best fit in Graph 1 cuts the axis close to the origin.