PASCO PS-2108 Dissolved Oxygen Sensor - Manual (Page 21)

Model No. PS-2108 Dissolved Oxygen Sensor
17 ®
Experiment 2: Photosynthesis and Oxygen Generation
with Aquatic Plants
Purpose
Explore the change in level of dissolved oxygen in water associated with photosynthesis of
aquatic plants.
Materials and Equipment Needed
• 2-PASPort DO sensors PS-2108
• 2-PASPort USB Links PS-2100
1
• USB equipped computer running DataStudio software
• 100 watt incandescent lamp (or equivalent)
• Lab stand(s)
• Masking Tape
• Paper
• 2-Test Tubes (25mm x 150mm)
• 1-1000 mL beaker
• 1 healthy sprig of Elodea
• Deionized or clean fresh water
Background
Plants carry out the process of photosynthesis when conditions are appropriate. Plants take in
reactants including carbon dioxide, water, and energy in the form of light. A waste product
from the photosynthetic process is gaseous oxygen, which is released to the environment.
For aquatic plants, this gas is released into the water, increasing the amount of dissolved
oxygen present in the water.
The dissolved oxygen sensor is well-suited to monitor changing levels of molecular oxygen
in the aqueous environment of the Elodea plant.
Tips for success:
• Set up and run the experiment far ahead of time, so that the procedure is familiar.
• Use fresh Elodea (the growing tip will give the best results).
• Allow water to reach equilibrium, in terms of the dissolved gases (this may take up to 24
hours)
• Submerge the DO sensor so that the metallic band is below the surface of the water.
• Use a full beaker of water for the water bath to control thermal fluctuations.
• Set up: (Complete steps 1-4 in advance)
1. or other PASPort interface