Osmosis in Potatoes

The following experiment is a fun and easy way to see the effects of plant osmosis on a plant by comparing two different potatoes placed in different types of water

These are the materials needed to view osmosis in action:

potato setup
- 2 Potatoes

- 2 Plates

- Salt

- Water

- Knife
(Adult needed)


Fill both of the dishes with water and add about two tablespoons of salt to one of the dishes. Using the knife have a parent cut the potato in half lengthwise. Then Place each piece flat side down in to one of the plates of water. HAVE AN ADULT HELP YOU!

Pasted Graphic 1

Now simply let the two potato pieces soak in the water for a few hours. After this time has passed flip each potato over and look for differences.

Pasted Graphic 2
When looking at the potato pieces you can clearly see a difference between the two. Lets take a closer look at each of the potato pieces!

Pasted Graphic 5

This potato slice is the one that has been soaking in freshwater. Not much of a difference here, only that the potato is a little more rigid then before. This is because there is the more salt and other dissolved chemicals within the potato then the surrounding water. This means that the water will move into the potato.

Pasted Graphic 3

This potato slice is the one that has been soaking in saltwater. This potato pieces looks substantially different from the original and the other slice. It seems to have wilted, gotten very soft and flexible. Why did that happen?

It has to do with a process called osmosis. The potato is made up of tiny, living units called cells. Each cell is surrounded by a cell membrane which acts much as your skin does. It keeps the cells parts inside and keeps other things outside, protecting the cell.

While this membrane stops most things, water can pass through it. The water tends to move towards higher concentrations of dissolved chemicals. That means that if the water outside the cell is saltier than the water inside, water will move from the inside of the cell to the outside. As the water left the cell it was much like letting the air out of a balloon. As more and more of the cells lost water, the slice of potato became soft and flexible.