Will watering plants with heated microwaved water kill the plant?
No. This question comes up repeatedly because of a nonsensical email that has been circulating since about 2010. The email features pictures of plants supposedly watered either with microwaved water or with water that has been heated on a stove top. Supposedly this little research gem was carried out by a student as a science fair project. And guess what! The microwave watered plants wither while the others flourish! One can come up with all sorts of possibilities explaining why differences could exist even if a legitimate attempt were made to carry out such an experiment properly. Was the soil the same in the two plants? Were they given equal amounts of water? Could they have been exposed to different lighting conditions? Was there some difference in the seeds? But before even asking such questions how about asking if pictures can lie? Absolutely! It isn’t very hard to take a series of two plants side by side and ensure that one thrives while the other dies. All you have to do is water one and not the other. Of course the possibility that this is the way the pictures were created does not prove the case.
Heating water in a microwave oven does nothing other than raise its temperature. Any talk about “the structure or energy of the water being compromised” is plain bunk. Water has no structure other than an attraction between the partially positively charged hydrogens in one molecule and the partially negatively charged oxygen atoms in adjacent ones. As far as altering the energy of the water, well, yes, that’s what heat is all about. Anytime anything is heated in any fashion its energy content is increased. The idea that microwaving water somehow changes its properties for the worse is plainly absurd.
But absurdly implausible arguments don’t prove that the pictures are faked either. What proves it is the good old standard of science, reproducibility. Or lack of. And we have done that. We have watered plants with microwaved water, kettle boiled water and stove top boiled water, feeling pretty sill about it, but we did it. The results? As expected, no difference. We aren’t posting any pictures because, after all, how would you know that they are not faked. So here is the choice. You can take our word that the experiment cannot be reproduced, accept that science tells us that microwaves do nothing to water other than heat it, or take at face value some pictures in a circulating email that purport to show an effect that has eluded scientists around the world but was discovered by a student pursuing a science fair project. The choice is yours.