Why does a potato gain weight after being placed in salt water?

Question

Our class had to do an experiment on osmosis. We placed a potato cube into a salt mix water concentration for about 21 hours
and the cube gained weight. Our previous observations was that the cube lost weight. Can anyone explain why the potato cube would gain weight? Thx so much.

Answer 1

Water will try to pass through a semi-permiable membrane in the direction of the more concentrated solution. If the potato juice was more concentrated than your salt water solution, water would enter the potato piece. If the salt solution was more concentrated, water would leave the potato piece. Perhaps your two salt solutions were different concentrations?

When I say concentrated, I'm referring to total concentration of whatever may be dissolved, not just conc. of any salt that may be present.

Answer 2

The previous observations also being with salt water? If so, then I'd say you just made a mistake somewhere in your weighing or something.

If the previous observations were fresh water, then I would say that salt water over fresh helps bring water in. For a similar concept, look at "brining" chicken and turkey. Brining is to soak it in salt water, and it helps draw water into the food.

So - difference between fresh and salt - similar to brining.
Just one experiment off of all salt water experiments, probably experimental error (if nothing else changed, e.g.: type of potato, rough age, density, weight, etc.)