Lab 12 - Dissolved Oxygen & Aquatic Primary Productivty.
Ask to DESIGN an experiment to measure the effect of salinity on the solubility of oxygen in water. What variables would need to control?
To design an experiment on measuring the effect of salinity on the solubility of oxygen in water, there are several variables that need to be controlled. Here's a step-by-step guide on how to design this experiment:
1. Research and Background:
Start by researching the existing knowledge on the relationship between salinity and the solubility of oxygen in water. Understand the factors that influence solubility and any previous experimental findings on this topic.
2. Hypothesis:
Develop a hypothesis based on your research. For example, hypothesize that as salinity increases, the solubility of oxygen in water decreases.
3. Experimental Setup:
Now, let's outline the experimental setup. You will need at least three identical containers to hold water samples, a source of oxygen, a method to measure dissolved oxygen, and varying levels of salt to modify the salinity. Here's a potential experimental design:
a. Containers: Use three or more identical containers, such as beakers or transparent bottles, to hold water samples. Label them as Control, Low Salinity, Medium Salinity, High Salinity, etc.
b. Water samples: Use distilled or deionized water to eliminate any existing dissolved oxygen. Fill each container with the same volume of water, ensuring consistency.
c. Salinity levels: Prepare solutions of varying salinity to simulate different concentrations. For example, you can use measured amounts of salt (NaCl) to create low, medium, and high salinity solutions. The control container should contain no added salt.
d. Oxygen source: Provide a controlled source of oxygen to each container. One practical option is an oxygen diffuser or bubbler, which injects a consistent flow of oxygen into the water.
e. Measurement of dissolved oxygen: Use an oxygen sensor or a dissolved oxygen meter to measure the levels of dissolved oxygen in each container. Record the measurements at regular intervals.
4. Controls and Variables:
To ensure a reliable experiment, it is crucial to control and manipulate specific variables:
a. Independent variable: The independent variable in this experiment is salinity. Control the salinity by varying the amount of salt added to each container.
b. Dependent variable: The dependent variable is the solubility of oxygen in water, measured as dissolved oxygen concentration (e.g., in mg/L or ppm).
c. Control variables: Keep other factors constant throughout the experiment to ensure that any observed changes in dissolved oxygen are due to changes in salinity. Control variables may include temperature, light exposure, stirring/agitation, and the quality of water used.
5. Data Collection and Analysis:
Collect data by measuring the dissolved oxygen levels in each container at regular intervals. Record all observations carefully, including the time, date, and environmental conditions.
Once the experiment is complete, analyze the data using appropriate statistical methods. Compare the dissolved oxygen levels among the different salinity levels and determine if there is a significant relationship.
6. Conclusion:
Finally, draw conclusions based on your experimental results and evaluate whether your hypothesis was supported or disproven. Discuss the implications of the findings and suggest further areas of research if applicable.
Remember to consult relevant scientific literature, follow appropriate safety guidelines, and consult with a knowledgeable instructor or mentor when conducting experiments.