Photosynthesis Experiment

Photosynthesis Experiment
Introduction
Photosynthesis is a process used by plants, making inorganic molecules into organic molecules (food) using sunlight.

Carbon dioxide + Water (mainly from rain)  Glucose + Oxygen

From this process, carbon dioxide comes from environment. Glucose, as a product is used to make energy for growth. Lastly, the oxygen is a waste product in this chemical reaction, which become part of the Earth’s atmosphere. At this experiment, carbon dioxide and water were replaced by ‘Sodium hydrogen carbonate’ because this led to simpler procedures than using carbon dioxide and water separately.

During photosynthesis, leaves only accept certain wavelength of light. For instance, most of leaves reflects radiation and receive blue and red colours. This happens due to colour of leaves. Generally, most of plants’ leaves are green and green colour reflects certain type of radiations. The green colour comes from chlorophyll, which contains photosynthetic pigment. It is mainly located at inside chloroplast1, parts known as grana and stroma.
 Structure of chloroplast - Granum is a singular form of grana.
Research Question ‘How does the amount of perceived power of light (equivalent to a power of sunlight) affects the process of making inorganic molecules into organic molecules?
Hypothesis
Higher light intensity will lead to faster growths of plants
Apparatus List
Stop watch
Leaf (Laurus nobilis, Laural leaf2)
Corer
3 Syringes (10ml each)
40-watt lamp
1 metre long ruler
Beaker (Contains Sodium Hydrogen carbonate, 0.2% concentration)

Variables
Independent Variable - Distance of each syringe from the light source (20 cm each, ’20 cm, 40 cm and 60 cm) - Measuring time of disc floating
Dependent Variable - Time of each leaf discs float
Controlled Variable - Size of each leaf disc (r = 0.5 cm) - Number of leaf discs in each syringe (10 discs) - Concentration of Sodium hydrogen carbonate (0.2%) - 10 ml of Sodium hydrogen carbonate in each syringe - All leaf discs must be sank - Same volume (10 ml) of each syringe - Same type of leaf disc (Laurel leaf)
Uncontrolled Variable - Temperature of Sodium hydrogen carbonate, external temperature

Procedure
1. Take 10 leaf discs with corer (r = -0.5cm)
2. Put 10 leaf discs inside each syringe
- 3 syringes as total (30 leaf discs as total)
3. Insert 10ml amount of Sodium Hydro carbonate into each syringe
4. Cover the tip of syringe and push plunger to sink all leaf discs, which is inside the syringe
5. Locate each syringe by 20 cm each from the light source

Light intensity = d = distance from the light source

6. Locate light lamp at edge of the ruler and initiate timing with a stop watch once turning the light source on.
Distance
Units for Timing – HH:MM:SS
Attempts
#1
#2
#3
#4
#5
#6
#7
20 cm
0:13:57
0:15:28
0:11:23
0:15:10
0:17:35.46
0:10:44
0:14:20
40 cm
0:50:12
0:46:21
0:46:51
0:48:26
0:42:28.55
0:58:26
0:50:02
60 cm
1:40:11
1:32:26
1:00:44
1:37:50
0:59:25
1:43:56
1:24:36
Data Table
Distance
Units for Timing – Converted from Hour : Minute : Second into Seconds
Attempts
#1
#2
#3
#4
#5
#6
#7
Average (Sec)
STD
20 cm
837
928
683
910
1055
644
860
845.29
142.68
40 cm
3012
2781
2811
2906
2548
3506
3002
2938.00
296.11
60 cm
6011
5546
3644
5870
3565
6236
5076
5135.43
1109.07

- Based on table, ’60 cm’ section shows highest standard deviation. On the other word, it shows most dispersion compared to other sections (20 cm and 40 cm).
Conclusion
Based on data gathered from the experiment, higher light intensity (or closer to the light source) provides faster growth. This supports the hypothesis of this experiment.

However, there was some dispersion of time records at each section. Especially the syringe with leaf discs gain more distance from the light source, it showed higher dispersion of data.
Evaluation
Leaves were not fresh enough to gain data with higher accuracy. According to the lesson, the leaves were collected on Nov/18 lunchtime and this experiment had proceeded on Nov/19, after 2:30PM. Using fresher leaves could have provided better results such as smaller standard deviation.

There could be some size differences between each leaf discs (estimation, around 0.2cm difference) due to external variables such as hand shaking issues.

Controlling the amount of sodium hydrogen carbonate could have some differences (estimation, around difference) due to similar variables as previous issue.

Bibliography
.

Bibliography: .