. Explain why the below phenomenon occurs:
You have a sample of a fiber made of polyvinyl alcohol. To one end of the fiber, you tie a weight of 200 grams. Now you immerse the end tied to the weight in a beaker full of water such that only the weight and a portion of the fiber is immersed. To your surprise, the observation is that, as long as the weight remains suspended in water, a stable situation exists. But when the weight is rested at the bottom of the beaker, the fiber dissolves
The most likely scenario is that, due to the weight pulling down the fiber, the PVA molecules are stretched and align better along the fiber direction. This will help PVA chain to pack tightly and reduce the diffusion coefficient of water. Upon removal of the weight, the molecules relaxes and water can diffuse faster into the fiber and dissolve the fiber. However, even under the weight, the water diffusion only slowed. Therefore, if you keep this experiment long enough, the fiber should dissolve eventually.
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