Setup Started: 30 April 2007
Starting Date: 30 April 2007
Current Status: Completed 30 May 2007, Week 5

This page is a thorough description of our study. If you would like a brief summary of the experiment see the summary of experiment page.

• Introduction and annotated directory

Problem
Hypothesis
Experiment design
Observations and data
Conclusion

For a history of why microwaved water became a topic of interest please see the detailed problem section of our plant experiment.

Our previous experiment, Does cooled microwaved water harm aquatic life?, indicated that microwave water might affect algae growth because the tank with microwaved water suffered algae blooms during the 13 week experiment. Of course, with only one experiment and one control, our evidence only begs for more experimentation. In itself, the evidence is too weak to draw any conclusion. There are too many variables that affect an aquarium ecosystem to say with any confidence that microwaved water caused, or somehow help triggered, the algae blooms.

With this in mind, I asked my class if they would like to tackle the question of microwaved water affecting algae growth with a larger sample. They were eager to explore this problem further, and so this experiment was designed to answer this question:

Does cooled microwaved water affect algae growth?

Students were asked to write their hypotheses based on the evidence (as weak as it is) from the previous experiment. They were encouraged to be thorough in their defense of their position. If they felt the algae blooms from the previous experiment were unrelated to the microwaved water, they were asked to suggest other causes. We brainstormed and shared ideas together before writing hypotheses.

Microwaved water will:

Here is an example of a hypothesis in favor of algae growth spurred by microwaved water:

Here is an example of a hypothesis stating that microwaved water will have no affect on algae growth:

We will maintain 48 twelve ounce cups with identical gravel and water level. Twelve cups will serve as our control, and twelve will be the experiment subjects.

This experiment will be a double blind study. Tap water will be used throughout the experiment. It will be treated with API Tap Water Conditioner to remove chlorine and hard metals. The water will be placed in jugs by a third party, and labeled A and B. Which jug contains the microwaved water will be determined by a coin toss. Each student will care for a pair of cups, one labeled A and one labeled B. Each student will be responsible for photographing and recording data for their pair of cups.

Gravel and plant clippings will be added to each cup. Then the cups will be filled with equal amounts of water (jug labels matched to cup labels, of course), and the top of each cup will be covered with plastic wrap to reduce evaporation. The cups will be exposed to light 24 hours a day.

Base on our photographic evidence and visual observations, we will attempt to determine if there is a significant difference in the growth of algae between group A and group B cups.

Photographic observations
Photographs taken at 7 day intervals (last update 30 May 2007)

Microwaved water does not affect algae growth. Each student determined which cup grew more algae, and then we tabulated the results on the board. Cup A and cup B tied (7 cup As had more algae, 7 cup Bs had more algae out of the cup pairs). There were 10 pairs of cups that the students decided had the same amount of algae.

The microwaved water was in cup A. If microwaved water affected algae growth, we would have expected a majority of the cup As to have a noticeable difference in their algae growth overall, and this was not the case. Some other variable was causing the algae to grow.