Aristotle’s hypothesis was not fully correct. Plant material comes partly from the soil, but also from air and water. A logical experiment is to weigh the dry soil in a pot before planting a seed in it. The grown plant plus the dry soil remaining in the pot will weigh much more than the original seed and its dry soil. One should ideally perform the experiment in a closed system to track the weight of water added, to recapture evaporated water, and to estimate the weight of air taken in by the plant.
Work Step by Step
To test a scientific hypothesis, one should conceive of a test that could prove the hypothesis to be incorrect, then carry it out.