Osmotic concentration

Imagine that you have a big bowl of fruit salad. All the different fruits (like apples, oranges, and grapes) have different amounts of sweet juices in them. If you put a bunch of salt on top of the fruit salad and stir it around, the juices in the fruits will start to mix together. However, the salt molecules won't mix in as easily because they are bigger and heavier than the fruit juices. So, the juices will start to "push" the salt molecules away from them to create their own little spaces.

This is kind of like what happens when we talk about osmotic concentration. The amount of stuff (like salt or sugar) dissolved in a liquid (like water) is called the concentration. When you have two liquids with different concentrations, they will try to mix until they are both the same concentration. But if they can't mix easily (like the salt in the fruit salad), they will start to push against each other and create their own spaces.

So, imagine that you have a cell (like a little bubble) that is filled with water and some other things (like nutrients or waste products). If the outside of the cell has more stuff dissolved in it than the inside of the cell, the water inside the cell will start to "want" to move out to try to balance the concentration. This movement of water across a membrane (like the outside of the cell) is called osmosis.

If too much water moves out of the cell, it can start to shrink or even burst! But if the concentration inside and outside the cell is balanced, the cell will be healthy and happy. So, scientists use the term "osmotic concentration" to talk about how much stuff is dissolved in a liquid and how it affects the movement of water across membranes.