WHAT IS OSMOSIS?
Osmosis is the process in which solvent (most often water) moves from the area of lower solute concentration into an area of a higher solute concentration through a semipermeable membrane.
Huh? Let’s break it down.
Let’s call our solvent water to keep it simple. Anything we dissolve in the water (sugar, salt) is a solute - there is less of it than a water and it will take on the characteristics of water when dissolved ( the whole solution is liquid). The more solute we dissolve, the higher will be the concentration of our solution.
WHY DOES THE SOLVENT MOVES FROM LOWER TO HIGHER SOLUTE CONCENTRATION?
Think of the membrane as a wall with gaps (it’s semipermeable!). When solutions on both sides of the wall have the same concentration of solute, nothing interesting happens - there is the equal probability water molecules will move from each side of the wall so in the end concentration will stay the same.
However, if we increase concentration on one side of the wall, for example, add salt to one side - water molecules will now move from the “normal” side into the salted side much more.
The mechanical explanation is that molecules of salt are blocking the movement of the water molecules so they are less likely to move from that side. The chemical explanation is that salt molecules consist of ions - Na+ and Cl-. Since water molecules are also partially charged they are attracted to salt molecules and therefore don’t move through the membrane.
WHY IS OSMOSIS IMPORTANT?
Osmosis is essential for the survival of all living organisms. It allows nutrients and minerals to move inside the cells and also for waste to move out of the cells. For example, plants absorb water from the earth through this process.
MATERIALS NEEDED FOR THE GUMMY BEAR OSMOSIS EXPERIMENT:
- Gummy bears (gummy candies)
- Spoon of salt
- 3 glasses
- Vinegar
- Water
INSTRUCTIONS ON GUMMY BEAR OSMOSIS EXPERIMENT:
Check the video at the beginning of the article to see how to conduct this experiment. We used three types of solvent (water, salt water and vinegar) but you can experiment with any type of solvent.
- Take 4 gummy bears (one for every type of solvent, +1 for comparison)
- Gummy bears are excellent for this experiment because they are made out of sugar, water and gelatine. Gelatine doesn’t dissolve in water, but it allows water to pass through so it functions as a semipermeable membrane.
- Prepare your mixtures: put pure water in one glass, water with a spoon of salt into other, and vinegar into third (or experiment with different mixtures).
- Put 1 gummy bear into each solution. Leave one on the side so you can compare afterwards.
- Leave it for a few hours. Check every 3h to see changes.
After 9h, we observed that gummy bear left in the pure water got much bigger than in the other solutions. Gummy bear in the salted water got just a little bit bigger. Osmosis at work! Salted water had much higher concentration than the pure one, so less water went into the gummy bear (in gummy bears there is some water, but not much, so the concentration is very high).
In vinegar, the gummy bear got bigger, but it also started to fall apart, and that’s because of the acid in vinegar which can dissolve gelatine.
What kind of solutions did you use and what are the results? Tell us all about your experiment in the comments!
WHAT WILL YOU DEVELOP AND LEARN?
- Chemistry and biology knowledge
- What is osmosis and how does it work
- Scientific method and conducting an experiment
If you are interested in more fun experiments about particle movement, you can try a simple Diffusion demonstration experiment.
And if you’re interested in more fun chemistry activities, check out Apple Oxidation Experiment and How to make sugar crystals.
