After I have done this, I will position each syringe 5cm apart on one another starting at 0cm and finishing at 20cm. I will time how long it takes for each leaf disc in each syringe to rise using a stopwatch and record all my results.
After preliminary work I have discovered problems with my original plan. The lamp is not the only source of light for each syringe. There is sunlight coming in through the window, providing extra light. Some syringes are in the shade so they are not receiving any sunlight making this an unfair experiment. To deal with this problem, I will close the blinds in my experiment.
Another problem is that, the original plan was to have one stopwatch and concentrate on one syringe until all of the leaf discs in it had rose. This took way too long. To solve this problem, everyone in my group will have a stopwatch and will have to concentrate on their own syringes. This will save us a lot of time.
Also to make sure that the leaf discs do not get stuck to each other or the syringe we will shake the syringes every 2 minutes.
I predict that the syringe containing leaf discs nearest to the light will photosynthesise the quickest and the one furthest away will photosynthesis the slowest. If not, the leaf discs nearer to the light will photosynthesise better than the ones further away from the light. Light is converted to chemical energy. Chlorophyll absorbs light energy and starts a chain of steps that result in the production of ATP, NADPH, and oxygen (through the splitting of water).The more light energy a plant receives, the more it can turn it into chemical energy so the more it will photosynthesise. If a plant received no light at all then it would die.
Analysis
The graph tells me that photosynthesis occurs more when the leaves are closer to the light. The further away the leaves were away from the light, the less photosynthesis occurred.
The graph increases at an increasing rate. It is a curved line.
My graph tells me lots of light is better than little light for a plant to photosynthesise and that the syringe furthest away from the light will photosynthesise the slowest. I can explain this by showing you the word equation for photosynthesis:
Chlorophyll + SUN LIGHT ENERGY
CARBON DIOXIDE+ WATER >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> =GLUCOSE + OXYGEN
Green plants have a food-making process called photosynthesis. Photosynthesis means putting together with light. Your plant needs light, carbon dioxide and water to show that photosynthesis has happened. Green plants use energy from light to combine carbon dioxide and water to make food. Our food comes from the energy-converting activity in green plants. Green pigments called chlorophyll absorb the light used in photosynthesis. Chlorophyll is in small bodies called chloroplasts, that are in plant leaves. In chloroplasts, light energy splits water molecules into hydrogen and oxygen atoms. Then in complicated steps, the process of photosynthesis is completed. So as you can see photosynthesis simply cannot occur without light.
If the plant is receiving lots of light then photosynthesis will occur quicker and better. If the plant is receiving less light then photosynthesis will not occur as well.
Although I cannot explain why the leaves in 2nd syringe rose the quickest. There is no scientific evidence to say that this syringe could be a reliable one. All the results from this syringe must be anomalous.
My prediction was that the leaves which were in the syringe closest to the light would photosynthesise quickest and that the one furthest away would photosynthesise the slowest. My graph does not quite agree with this, as the leaves 2nd closest to the light photosynthesised quicker, then followed by the leaves closest to the light. Although I did predict correct that the leaves furthest away would photosynthesise the slowest. I also predicted correctly that the leaves closer to the light would photosynthesise better than the leaves further away.
Evaluation
I don’t think my procedure was good enough and that the results were fairly accurate, but not accurate enough.
I know this because of my error bars. My first error bar is very long, mainly because of the last leaf in that syringe. Apart from the last leaf, all the other results are quite close together. My most reliable result was the syringe 10cm away. The error bar here is very small and all the results are close to the average. The syringes 15 & 20cm away are pretty reliable too. The results are around the average and the bars aren’t too long.
My syringe 5cm away is pretty reliable according to my error bar but I will trust scientific evidence and call this syringe an anomalous one.
When a leaf would rise, sometimes we couldn’t tell if one leaf was rising on its own or whether it was stuck to another. This distracted our attention and meant we didn’t get the exact time that the leaf/s had risen. When a leaf pulled another one up with it, it led to inaccurate results. The leaf that was pulled up, would possibly have taken some more time to rise if it hadn’t been pulled up. We shook the syringes every few minutes, this didn’t solve the problem.
Another mistake is that when we were writing down the results, the writing wasn’t very clear because the person writing down the results would’ve been busy timing the rising leafs. And then when we copied up the results into our own books, we could’ve copied them down wrong if we weren’t able to read the person’s writing, which I think may have happened.
In addition sometimes we made mistakes with the stopwatches. We may have accidentally pressed the split button which led to inaccurate results. Not everyone fully knew how to use the stopwatches properly.
During the experiment, not everyone was paying full attention to the leafs as it took quite long to do. This possibly led to even more inaccurate results.
My anomalies and explanation for each one: The leaf discs in the second syringe rose quicker than the discs in the first syringe. The whole syringe was completely anomalous, I know this because there is no scientific evidence to explain why this may have happened. The more light there is the better a plant will photosynthesise. The reason for this anomaly could possibly be that there was too much carbon dioxide in the syringe. Maybe we didn’t create a good enough vacuum in it making the leaf discs rise too quickly. If we didn’t mix the water properly when we put it in the syringe, there could be more sodium hydrogen carbonate in there.
Another anomaly was the last leaf disc to rise in the first syringe. It took over 18 minutes to rise, which was far longer than it should’ve took. There could’ve been something wrong with the leaf disc. I know this is an anomalous result because all the other leaf discs in this syringe had risen pretty quickly. Maybe this disc didn’t have much chlorophyll in there, meaning that the disc wasn’t absorbing the light properly. This disc could’ve been from a bad part of the leaf that it was originally from.
When we set up the lamp we used a block of glass filled with water as a heat block. This was done well as it meant the only thing we changed in all the syringes was the amount of light they received. We cut out the leaf discs from the same type of leaf with the same leaf cutter and put the same amount of discs into each syringe. This was also well done because it meant all the discs were the same size and everything was fair. We also made sure that the water inside the syringes had the same amount of carbon dioxide. Then we created a vacuum in each of the syringes which was done well by everyone in the group, possibly with the exception of the second syringe. We put the syringes 5cm apart, this was a good distance to put them apart because it meant that there would be no accidents but we still got decent results. Everyone had their own stopwatches and their own syringe to keep an eye on which saved us time.
I think the whole experiment needs repeating, possibly 3 times, which would give us very accurate results and an average. The results this time were not accurate enough e.g. the leafs in the second syringe rising quicker than the first.
Next time maybe we could have more leaf discs in each syringe, which could make our results more accurate. For example, the 3rd or 4th leaf in the syringe 10cm away rises quicker than the 3rd or 4th leaf in the 5cm syringe. It is quite a good possibility that the rest of the leaves in the 5cm syringe rises quicker than the rest of the leaves in the 10 cm syringe. This would mean that 8 results are accurate and 2 are not, giving us reliable results. If there were only five leaf discs in each syringe, then only 3 would be accurate and 2 would not, giving us unreliable results.
We could maybe have more syringes e.g. one at 0cm, another at 2.5cm, another at 5cm etc. This is very likely to lead to more accurate results, although we would have to be careful to ensure that there were no accidents. For example, if the leaf discs in the syringe 15cm away rose quicker than the leaf discs 10cm away, The syringe 12.5cm away could have rose quicker than the 15cm syringe.
If we had better stopwatches this would help a lot. If there was a stopwatch which had a button that we could press every time a leaf rose, and then at the end we could go back and check all the times that we had a pressed the button. This would be very helpful and make our results more accurate. It would mean that we wouldn’t even have to look at the stopwatch to tell the time, every time a leaf rose, all we’d do is a press a button.
My results were all fairly accurate, except the results with the second syringe. This made the overall accuracy of my results weren’t as good as good as they could’ve been. Therefore my results weren’t as reliable as they could’ve been.
My conclusion, on the whole, is that leaves closer to the light photosynthesise better than leaves further away is quite accurate. However it is not accurate that the syringe 2nd closest to the light photosynthesises quickest, as my results tell me. If we were to repeat the experiment several times, then it would be quite difficult to measure out 0.5g of the sodium hydrogen carbonate accurately each time, as this is a very small amount.
If I was to do a further investigation. I would then set up a lamp with a heat diffuser, giving us only one variable, which is light (same as my experiment). I would use 5 elodea plants and place each one in water which would have the same amount of carbon dioxide in each. I would ensure this by using the same amount of sodium hydrogen carbonate in the water. I would also use the same amount of water for each plant. Each plant would roughly be the same size. I would place each plant 5cm away from each other. Then I would cut the end of the plant. This is so that bubbles of oxygen rise when the plant photosynthesises. If there was any other source of light e.g. windows, I would close the blinds or curtains so that the lamp is the only source of light for the plant. All of this would make this experiment fair. Then I would count the number of bubbles coming out of each plant per minute. The plant which released the most bubbles would be photosynthesising the most.
This experiment would be useful if I did it. If the plants closer to the light photosynthesise better than the plants further away from the light, it would prove that my results in my previous experiments were quite good.
What would be very interesting is that if the plant 2nd closest to the light photosynthesises better than plant 1st closest to the light by releasing more bubbles. This would be identical to my results in my previous experiment and would be going against my scientific knowledge and other scientific evidence. And if the same thing kept happening in different experiments as well as mine then this would be a new discovery.
