Question

Why does the stain move across the slide when the paper towel is applied?

Answer 1

Water based liquids are polar which means the hydrogen and oxygen molecules are slightly positive or negative. One of the causes of being a polar molecule is that the water based liquid is cohesive, this allows the liquid to stick to itself. Along with cohesion is adhesion which allows it to stick to other substances. The liquid sticks to the paper towel and pulls itself along as if it were tied together until the full area is absorbed. But don’t quote me on it ;).

Answer 2

Not very sure, but this is probably because the stain is much more dried up and already sticked onto the surface, rather than the paper towel that simple brushed by it for the couple of seconds used in attempt to wipe the stain.

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