Capillary Action

Water can actually move upward against gravity in narrow spaces. This is called capillary action. You can see it when you dip a paper towel in water and the water climbs up the towel. Capillary action is how plants move water from their roots up to their leaves.

How It Works

Capillary action happens because water molecules are attracted to other materials. When water touches a narrow tube or thin space, the water molecules cling to the walls. They pull more water molecules up behind them. The narrower the space, the higher the water can climb.

Capillary Action in Nature

Plants depend on capillary action to survive. Water in the soil is pulled up through tiny tubes in the roots and stems. This helps carry water and nutrients all the way up to the tallest leaves. Trees over 300 feet tall use capillary action along with other forces to move water from roots to crown.

Fun Facts

• You can see capillary action by putting a white flower in colored water. The petals slowly change color.
• Paper towels are designed with tiny spaces between fibers to maximize capillary action.
• The wax in a candle is pulled up the wick to the flame by capillary action.

Did You Know?

If you put thin glass tubes of different widths in water, the water rises highest in the narrowest tube. In a tube just 0.1 millimeters wide, water can climb over a foot high through capillary action alone!