Starting date: 5 Jun 2006
Completion date: 15 Jun 2006

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

A parent informed me of an email that was making the rounds which pointed to a website that claimed microwaved water kills plants. I immediately saw an opportunity to have my students experience science as it is practiced by scientists. With only 11 days left before summer break, we set out to see if we could replicate the experiment while improving on the design.

I conducted an internet search and found the original website that claims, after nine days of receiving cooled microwaved water, a plant died. The website displayed photographs of the two-plant experiment. The pictures show that the experiment plant dies while the control (watered with non-microwaved water) remains healthy. I then found several web forums responding to the claim, but found nothing from the scientific community on this subject (admittedly, my search was brief).

Obviously, with a sample size of one, the original experiment is only fuel for further investigation. In addition, I believe it has serious data problems. Taking a cue form Mahatma Kane Jeeves, one of the many forum members I came across discussing this experiment, I downloaded pictures Day 1 and Day 5 from the original experiment, popped them into Photoshop, laid them over one another, set the top level to 50% transparency, and found them to be taken only moments apart (as opposed to 5 days as claimed). I would have stopped here and dismissed the experiment as a fraud if I had not thought that replicating it would provide an excellent opportunity to show my students the self-correcting nature of science.

Replicating the experiment with my students intrigued me for several reasons.

Knowing only two weeks remained in the school year, I based our problem on the 9 day experiment:

Does watering a plant with water that has been microwaved kill the plant within 9 days?

Each student came up with his or her own hypothesis. After brainstorming it was decided that there were four basic choices.

Microwaved water will:

This was a double blind study. Neither my students, nor myself, knew which water jug contained the microwaved water.

The plants were potted and the pots were marked with a number (1 through 48). Each student drew two numbers from a box, then the numbers were match to the corresponding number on the plant pot. Each student received two plants in this way (two students doubled up, as we had 22 students and 24 pairs of plants). The plant pots were labeled A and B based on the order each student received them (first = A, second=B).

The next step was completed by a third party so that I did not know which jug contained the microwaved water. The water was microwaved in a 2 quart Pyrex measuring cup for 18 minutes (we are using gallon jugs, so this process had to be repeated twice). After the water was allowed to cool at room temperature, it was placed in its original plastic jug. Then enough of the water that was not boiled was removed from its plastic jug so the water levels matched (due to evaporation of the boiled water). The jugs were labeled A and B based on the flip of a coin (A = microwaved water if heads, B = microwaved water if tales).

The students worked in teams. First they photographed their plants, then each team would check their plants to decide if water was needed by using a Rapitest Mini Moisture Tester. After watering, the students placed the plants back on the classroom window ledge. A camera was left on a tripod, and the plants where placed on marked lines so the photographs showed the same angle and position of the pot for better comparison. During the experiment the tripod was accidentally bumped many times, but this did not compromise the experiment.

After ten days the students met as a group and studied their data to come to a conclusion.

Only 6 sets of Day 1 and Day 10 pictures are presented here. The samples below were picked before the results of the experiment were known.

To see all 24 paired sets go to the detailed observations page. If you're really data hungry use the plant gallery where 24 sets of 8 pictures can be found.

Plant A is always to the left.

Pair 1, Day 1

Pair 1, Day 10

Pair 8, Day 10

Pair 8, Day 1

Pair 10, Day 1

Pair 10, Day 10

Pair 17, Day 10

Pair 17, Day 1

Pair 21, Day 1

Pair 21, Day 10

Pair 24, Day 1

Pair 24, Day 10

All of the plants grew well. The students and I felt that it was impossible to tell any difference between the health of group A plants and group B plants. Our only fatalities were 1 plant A and 2 plant Bs, which suffered from lack of water over the weekend (see the weekend drought page).

The class concluded that the microwaved water had no influence on the plants, because all of the plants (except the 3 that died due to lack of water over the weekend) were growing equally well. We could see no differences in health between the group A and group B plants.

The container containing the microwaved water was in jug A.