To discover what causes your hands to get wrinkly in water.
1.) Make a saturated salt solution by dissolving as much salt as you can in a cup of water. Fill another cup with fresh water from the tap.
2.) Submerge one hand in the salt water and the other in fresh water fro 20 minutes.
Observer both hands.
You should notice that your hands gets wrinkly from soaking in freshwater, just like being in the bathtub. However, the hand that was soaking in salt water will not be wrinkly at all! Every cell in the skin of your hands contains a semi permeable membrane, which allows some substances to enter the cell, but not others. Water can freely pass in and out of the cells of your skin.
Whether water passes in or out depends on the concentration of salt outside of the cells. If your cells are surrounded by a solution that has a greater concentration of salt, water will pass from these cells to the outside solution in and attempt to equalize the concentration.
This passage of water through a semipermeable membrane is known as osmosis. IF the concentration of salt is greater within the cells than outside, water will move into the cells. Water will always move in the direction of the greatest salt concentration, in attempt to dilute it.
When placing your hand in tap water the solute concentration in the cells of your skin is greater than that of the tap water. The cells have a greater concentration of dissolved solutes that the water surrounding them. The cells are hypertonic to the surrounding solution. As a result, water will flow into the cells in an attempt to equalize the concentrations. This makes the skin wrinkly.
However the solute concentration of the salt water is greater than that of the solute concentration in the cells. The cells have a lower concentration of dissolved solutes than the salt solution surrounding them. The cells are hypotonic to the surrounding solution. In an attempt to equalize the concentrations, water will actually leave the cells of your skin, making your skin fell a littler tighter. This is how bath salt works, which prevents your skin from getting wrinkly as you soak in the tub. Remember to check your fingers the next time you swim in the ocean.