Question

Potato slices become crisp in plain water but become flaccid in strong salt solution. Why?

Answer 1

Hint:- Osmosis simply put, is a phenomenon in which molecules of a solvent move from a less concentrated solution to a more concentrated one, until and unless the concentrations equalize on both sides of a semi or partially permeable membrane. It needs just no energy, so this process is a passive one.

Complete step-by-step solution:-
If seen relevant to the question, basically there are 3 forms or types of solutions :
1. Hypotonic Solution,
2. Isotonic Solution,
3. Hypertonic Solution,
If we place a substance inside any hypertonic solution, it loses water. Thus creating a room between the cell’s membrane and the cell’s wall; and as a result, that cell turns flaccid (soft or floppy) or undergoes plasmolysis. This is called Exosmosis. Amidst this, the cell loses track of its turgidity.
While, if we place a substance inside any hypotonic solution, the molecules of the solvent move towards the cell, thus making the cell turgid or or making it undergo deplasmolysis. This is called Endosmosis.
Potatoes contain both starch and water. So, when potato slices are placed in strong salt solutions they shrink, i.e the water inside the slices diffuses from the areas of lower concentrations to the areas of higher concentrations.
Whereas, the slices placed in plain water slightly swell up and become crisp. As mentioned above, when a cell is placed in a hypotonic solution, the plant cell intakes water. And when the cell is fully inflated with water, it becomes turgid.

Note:-
- Water always moves into the higher concentration areas from the lower concentration areas.
- Another example from our daily lives is - when raisins are kept/soaked in water, they get puffed up.