Osmosis

water · science · cells · membranes

Water sneaks through. Osmosis is when water molecules move all by themselves through a special membrane to try to make two solutions equally salty. They're not being pushed by anything you can see, they just naturally move that way.

Membranes are picky. A selectively permeable membrane is like a bouncer at a club that lets tiny water molecules through but blocks bigger salt particles. This one-way filtering is what makes osmosis happen.

Nature loves balance. Water keeps flowing through the membrane until the salt concentration is the same on both sides. It's like nature trying to make everything fair and even.

Osmotic pressure works. If you push hard enough on one side of the membrane, you can actually stop the water from moving through at all. Scientists use this pressure measurement to understand how strong the osmosis force really is.

Concentration is what matters. Whether the dissolved stuff is sugar, salt, or anything else, osmosis depends only on how much is dissolved, not what it actually is. This is a special rule in science called a colligative property.