Question

What happens when raisins are placed in water at room temperature?

Answer 1

As the raisins are porous, through osmosis the water diffuses into the raisins making the raisins swell up.

Answer 2

When raisins (or any other dried fruit like figs and apricot) are placed in water at room temperature, the water molecules diffuse into them. As a result, they swell. In long term, the raisins are partly fermented along with spoiling.