How to Make an Osmosis Experiment for a Kids Science Project

Lead Image
  • 1 hours
  • Beginner
  • 0-20
What You'll Need
3 plastic cups
Self-adhesive labels

Explaining verbally to kids what osmosis is all about won’t have the same impact as setting up an osmosis experiment to actually show what you are trying to get across. Osmosis is the movement of water through a porous membrane, like the process by which trees absorb great amounts of water through their roots up to the highest leaves. There are many food items you can use to demonstrate quite well the process of osmosis, like eggs, baking soda, potatoes, carrots, and celery. Follow the simple steps below to create a science project related to osmosis using a potato and other simple household items.

Step 1 - Label

Put a label on each cup, and mark each as salt, sugar, and plain water. Fill the cups halfway with water and put them on a sturdy top where they can’t be knocked over.

Step 2 - Saturate

In the cup labeled sugar, stir in sugar until the solution reaches its saturation point and can’t take any more sugar. Then, do the same with the cup labeled salt.

Step 3 - Cut

Although younger kids can help with some of the steps, cutting the potato should always be done by an adult for safety’s sake. Cut three equal thin slices from the potato middle. Put one slice in each labeled cup and leave to sit for at least half an hour.

Step 4 - Look at the Results

Once enough time has passed, let the kids see what has happened to each potato slice in the different cups. The potato in the cup labeled salt has become very soft, the one in the sugar solution is also soft but less than the salt one, and the one in plain water has hardened.

Osmosis - A Simple Explanation

This demonstration shows what osmosis is about: the salt in the water made the small living units called cells in the potato slice lose their water through absorption, and so the slice wilted. The same thing happened to the potato slice in the sugary solution, but since the cells manufacture more sugar than salt, the slice did not get as soft as the one in the salt solution. As for the slice in plain water, the reverse took place and it became bloated when the water in the cup joined the natural water in the cells, giving it an overdose of water.

This process takes place in our bodies when we sweat in very hot temperatures or during heavy exercise and we lose a lot of water. This will raise the concentration of salts in the body and, by osmosis, drain our cells of their water. We reverse this by drinking plenty of water to dilute the excessive salts and removing them through sweating.