Osmosis Potato Experiment

Finished with your lesson on Osmosis but still confused? Then you need to perform this simple Osmosis experiment. All you need are some potato slices and water. Learn about osmosis with potato slices in this simple osmosis potato experiment.

What is Osmosis?

Osmosis is the process by which water or any other solvent moves towards a solution with a higher concentration through a semipermeable membrane. The molecules in the solution with a lower concentration move towards the solution with a higher concentration to equalize the concentration on both sides. Osmosis is how plants absorb water and nutrients from the soil.

A simple science experiment for kids like the Osmosis Potato Experiment helps kids understand the concept easily.

Read on to learn how to perform the Osmosis experiment using just potato slices:

Things You Need for the Osmosis Potato Experiment

If you leave cut slices of potatoes or apples or pears outside for a while, you’ll notice that they turn brown. Why do you think this discoloration occurs? When you cut these fruits or vegetables, it leaves the cells open. An enzyme present in the cells, polyphenol oxidase, reacts with the oxygen in the air and turns the fruit brown. But can you prevent the slices from turning brown and keep them fresher for longer? Let’s learn through this osmosis potato experiment.

Here is a list of things you’ll need to perform the experiment:

  1. 1 medium sized potato
  2. 2 – 4 tablespoons of salt
  3. Distilled water
  4. 2 medium sized mason jars or drinking glasses
  5. Knife

A Step-by-step Guide to Perform the Osmosis Potato Experiment

Follow these instructions to perform the experiment:

  • Step 1: Peel and cut the potatoes so you have wedges that are neither too thick nor too thin. Ensure that the potato wedges are roughly the same size. Note down the color of the freshly cut potato wedges and how they feel when you touch them.
  • Step 2: Pour 200ml of distilled water into one glass or jar. 
  • Step 3: Into the second glass, pour 200ml of distilled water and add 2-4 tablespoons of salt. Stir it well until the salt is completely dissolved.
  • Step 4: Add two potato wedges into each of the glasses and let them sit overnight.
  • Step 5: The next day, you’ll notice a difference in both the glasses. The potato wedges in the glass with the unsalted water have become bigger, while the wedges in the salted water have shrunk slightly.
  • Step 6: Take the potato wedges out of the unsalted water and try bending them. You’ll notice that it is firm and breaks but doesn’t bend. Additionally, it still has a white color like a freshly cut piece of potato.
  • Step 7: Now take the potato wedges out of the salted solution and try to bend them. You’ll notice the wedges have turned brown and bend easily without breaking.

The Science Behind the Osmosis Potato Experiment

Once you’ve performed the experiment, help your child understand the science behind the osmosis experiment. Here are a few questions and answers that will help children understand the behavior of the potato wedges in the two different solutions.

  1. Why did the potato wedges in the glass with plain distilled water become bigger?
  2. The potato wedges expand and become bigger because of osmosis. Potatoes are made of millions of cells and the cell walls act as a semipermeable membrane. The water molecules move into the potato through this membrane to balance the concentration levels. The water moving inside the potato cells causes it to expand and become bigger. 

  3. Why did the potato wedges in the glass with salt water shrink?
  4. Again it’s because of osmosis. The salt solution has a higher concentration and the water inside the potato moves through the cell walls to balance the concentration in the saltwater. Since the water moves out of the potato wedge, it shrinks and becomes smaller. This is also the reason why the potato wedge in the salt solution becomes less rigid and bends easily.

  5. Why did the potato wedges in the salt solution change color?
  6. The water moving out of the potato damages it’s cells, which causes them to release an enzyme called catechol oxidase. The enzyme in the potato cells reacts with the oxygen in the air and turns the wedges brown.

What Else Can You Use to Perform the Osmosis Potato Experiment?

Another cool way to see osmosis in action is to perform this experiment using grapes and raisins.

Here is a list of things you’ll need to perform the experiment:

  1. 2 – 3 raisins
  2. 2 – 3 fresh grapes
  3. 3 – 4 tablespoons of sugar
  4. 2 glasses of plain water

Follow these instructions to perform this experiment:

  • Step 1: Add the 3 – 4 tablespoons of sugar into one glass of water and stir it until all the sugar is dissolved. Then add 2 -3 fresh grapes into the sugar solution.
  • Step 2: Add 2 – 3 raisins to the second glass of water. Allow both glasses to sit for a few hours.
  • Step 3: After a few hours, you’ll notice that the raisins in the plain water have plumped up almost as if they are grapes. The raisins have a higher concentration of sugar, so the water moves into the raisins to balance the amount of sugar. This causes the raisins to expand and plump up.
  • Step 4: Meanwhile the grapes in the sugar solution have shrunk and almost look like raisins. The water surrounding the grapes has a higher concentration of sugar than water in the grape cells. So the water in the grape cells moves out to balance the level of sugar. This causes the grapes to shrink in size.

Can you use other vegetables or fruits to perform this experiment? Will sliced bananas or pineapples work the same way? The only way to know is to try. Looking for more cool science experiments to try with your kids? Check our kids learning section for more fun and informative science experiments.

Frequently Asked Questions on Osmosis Experiment

What is Osmosis?

Osmosis is the process by which a solution with a lower concentration moves towards a solution with a higher concentration through a semipermeable membrane to balance the levels of concentration.

Why does the potato in the salt solution shrink?

Potato cells also have water in them. The water in the potato tries to equalize the concentration by moving towards the saltwater. The loss of water causes the potato to shrink and also makes it bendy and less firm.