Regarding osmosis, why is it that when you drink softdrinks, you still feel thirsty?

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bandmanjoe | Middle School Teacher | (Level 2) Senior Educator

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Osmosis is diffusion of water across the semi-permeable cell membrane.  When you drink a soda, it has a higher salt content than does the water that is contained within you cells.  The water in your cells will diffuse, by osmosis, into the salt content of the soda, in an attampt to equalize the water concentration of the soda.  This is the same reason a person will die if they drink ocean water on a continual basis, the salt in the ocean water will force the fresh water content in your cells to diffuse out, leaving the cells in your body dehydrated.  Ultimately, a person can die of dehydration by drinking salt water.  It seems backwards, but that is what happens.  Another good example is to take a sliced carrot stick, which is normally crisp when you break it, and soak it in a solution of salt water for about 24 hours.  The next day, the carrot stick will be limp, because a good portion of the fresh water in the carrots cells diffused by osmosis into the salt water.

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