SchoolHouse

Have you ever noticed how water seems to climb up a paper towel all on its own? This is called capillary action.

Here's how it works, step by step:

Step 1: Water comes in contact with a thin tube (like the inside of a plant stem or a paper towel).

Step 2: Water molecules are attracted to the tube's surface. This pull is called adhesion — it grabs the water and pulls it upward along the walls.

Step 3: Water molecules are also attracted to each other. This is called cohesion. As the first molecules get pulled up by adhesion, cohesion drags more water molecules along behind them.

Step 4: The result? Water climbs up the tube — sometimes against gravity!

Trees depend on capillary action (along with transpiration pull) to move water from their roots all the way up to their highest leaves — sometimes over 300 feet! The thin tubes inside a tree trunk are called xylem, and they work just like tiny straws.