AP BIOLOGY

Detailed explanation-1: -A phenomenon called endosmosis takes place when raisins are placed in water for few hours. When raisins are soaked in water, they swell. All this is due to the process of osmosis. The water molecules pass the cell membrane of the raisins and the raisins thus get swollen.

Detailed explanation-2: -Raisins swell when it is put in water, because of greater concentration of salt inside the resins and the amount of water is less. When the raisins put in rainwater, the water from the surrounding diffuses into the raisins so the raisins swell up. The phenomenon involved here is endosmosis.

Detailed explanation-3: -Raisins swells because of osmosis. Solution outside the raisin has a higher concentration of water molecules. Therefore, water from outside enters the raisin through the process of osmosis and hence the raisin swells up when kept in water.

Detailed explanation-4: -Since, water flows from higher concentration area to lower concentration area (as per osmosis), water will flow out from raisins and enter the salt solution. Thus, raisins are shrinked in salt water. However, in case of normal water, swollen raisins will be obtained.