Leaf Disc Lab

Leaf Disc Lab

Hannah Gordon

Pd4 11-30-09

Number of disks floating with light source
Light source #1 (purple) / Light source #2 (green) / Light source #3 (red) / Light source #4 (normal)
Time (minutes) / raw / corrected / raw / corrected / raw / corrected / raw / corrected
1 / 5 / 0 / 9 / 0 / 6 / 0 / 6 / 0
2 / 6 / 1 / 10 / 1 / 6 / 0 / 6 / 0
3 / 6 / 1 / 10 / 1 / 6 / 0 / 6 / 0
4 / 6 / 1 / 10 / 1 / 6 / 0 / 6 / 0
*5 / 7 / 2 / 10 / 1 / 6 / 0 / 6 / 0
6 / *6 / 1 / *6 / -3 / *4 / -2 / *4 / -2
7 / 6 / 1 / 6 / -3 / 4 / -2 / 6 / 0
8 / 6 / 1 / 6 / -3 / 4 / -2 / 8 / 2
9 / 6 / 1 / 6 / -3 / 4 / -2 / 9 / 3
10 / 6 / 1 / 6 / -3 / 4 / -2 / 9 / 3
11 / 6 / 1 / 6 / -3 / 4 / -2 / 9 / 3
12 / 6 / 1 / 6 / -3 / 4 / -2 / 9 / 3
13 / 6 / 1 / 7 / -2 / 4 / -2 / 9 / 3
14 / 6 / 1 / 8 / -1 / 5 / -1 / 9 / 3
15 / 6 / 1 / 7 / -2 / 5 / -1 / 9 / 3
Number of disks floating without light source
Light source #1 / Light source #2 / Light source #3 / Light source #4
Time / raw / corrected / raw / corrected / raw / corrected / raw / corrected
1 / 7 / 0 / 7 / 0 / 5 / 0 / 10 / 0
2 / 8 / 1 / 7 / 0 / 4 / -1 / 10 / 0
3 / 9 / 2 / 7 / 0 / 5 / 0 / 10 / 0
*4 / 9 / 2 / 8 / 1 / 3 / -2 / 10 / 0
5 / 9 / 2 / 8 / 1 / 2 / -3 / 10 / 0
6 / 9 / 2 / 8 / 1 / 2 / -3 / 10 / 0
7 / 9 / 2 / 7 / 0 / 2 / -3 / 10 / 0
8 / 9 / 2 / 9 / 2 / 2 / -3 / 10 / 0
9 / 9 / 2 / 9 / 2 / 3 / -2 / 10 / 0
10 / 9 / 2 / 10 / 3 / 3 / -2 / 10 / 0
11 / 9 / 2 / 10 / 3 / 3 / -2 / 9 / -1
12 / 9 / 2 / 10 / 3 / 4 / -1 / 10 / 0
13 / 7 / 0 / 10 / 3 / 4 / -1 / 10 / 0
14 / 7 / 0 / 9 / 2 / 4 / -1 / 10 / 0
15 / 7 / 0 / 10 / 3 / 4 / -1 / 10 / 0

-Up until five minutes into the experiment the classroom lights had been on and some of the shades had been up so those were closed/turned off

-At six minutes we swirled the beakers to unstick some of the disks on the sides but it also caused some of the disks to sink

-Up until four minutes into the second part of the experiment we had only had the top of the beaker covered in foil so we then covered the whole beaker

Shown in the tables and graphs above there was not much change in the amount of floating leaf discs. Both the purple light and the normal light had disks that stayed fairly constant with a few outliers such as the negatives. It is not actually possible for there to be negatives but we started out with some of the disks already floating which is what caused the negative numbers to happen as some of the originally floating disks sunk. Some of the light sources such as purple and green had more disks floating once the beakers were covered than when the light was actually shining on them. This could mean that after sitting in the darker lights for a while the leaf disks started doing dark reactions. Both the red and the green light source graphs are fairly sporadic which could have been caused by the various limitations and errors.

Conclusion and evaluation:

There were a fair amount of errors made during this lab which makes a conclusion difficult. Based on the data gathered by my group I would conclude that the leaf disks absorbed the regular light the best since more disks were floating while the light was shining on them than when the beaker was covered by foil. With both the purple and the green light sources the leaf disks started to float more once the lights were turned off and the beakers were covered. This could mean that with these two types of lights the leaf disks did not do as much absorbing while directly under the light but rather performed dark reactions. The red light was clearly not effective as any of the others seeing as most of its data is negative meaning that the leaf disks did not do much absorbing of this light and just sank.

Some of the weaknesses encountered were that not all of our leaf disks were prepared so that they sank to the bottom of the beaker at first. Our group also misunderstood and at first did not completely cover the beakers with foil meaning that some light could have been affecting the leaf disks when it shouldn’t have.

Some limitations to this experiment were that light was coming in through the windows and from the lights for the first part of the experiment which could have affected the leaf disks. Also we ran out of time and were not able to go for as long as we should have which limited the changes we saw in out data.

Some improvements that could be made to this experiment are, we could have taken more time in preparing the leaf disks before we put them in the beakers. Also we could have had the shades drawn and the lights off right away before we started the experiment. And if we had had more time we might have been able to collect more effective data.