CAPILLARY ACTION - A spontaneous flow of liquid that doesn't require gravity to work - Capillary action is defined as the spontaneous flow of a liquid into a narrow tube or porous material. This movement does not require the force of gravity to occur. In fact, it often acts in opposition to gravity. Capillary action is sometimes called capillary motion, capillarity, or wicking. Capillary action is caused by the combination of cohesive forces of the liquid and the adhesive forces between the liquid and tube material. Cohesion and adhesion are two types of intermolecular forces. These forces pull the liquid into the tube. In order for wicking to occur, a tube needs to be sufficiently small in diameter. Examples of capillary action include the uptake of water in paper and plaster (two porous materials), the wicking of paint between the hairs of a paintbrush, and the movement of water through sand. Capillary action was first recorded by Leonardo da Vinci. Robert Boyle performed experiments on capillary action in 1660, noting a partial vacuum had no effect on the height a liquid could obtain via wicking. A mathematical model of the phenomenon was presented by Thomas Young and Pierre-Simon Laplace in 1805. Albert Einstein's first scientific paper in 1900 was written on the subject of capillarity.

In paper chromatography, solvent moves up paper via capillary action, moving pigment molecules with it

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Capillary Action

Definition and Examples

A spontaneous flow of liquid that doesn't require gravity to work

By Anne Marie Helmenstine, Ph.D.

Capillary action is defined as the spontaneous flow of a liquid into a narrow tube or porous material.

This movement does not require the force of gravity to occur. In fact, it often acts in opposition to gravity.

Capillary action is sometimes called capillary motion, capillarity, or wicking.

Capillary action is caused by the combination of cohesive forces of the liquid and the adhesive forces between the liquid and tube material.

Cohesion and adhesion are two types of intermolecular forces.

These forces pull the liquid into the tube. In order for wicking to occur, a tube needs to be sufficiently small in diameter.

Examples of capillary action include the uptake of water in paper and plaster (two porous materials), the wicking of paint between the hairs of a paintbrush, and the movement of water through sand.

Fast Facts: History of Capillary Action Study

·      Capillary action was first recorded by Leonardo da Vinci.

·     Robert Boyle performed experiments on capillary action in 1660, noting a partial vacuum had no effect on the height a liquid could obtain via wicking.

·      A mathematical model of the phenomenon was presented by Thomas Young and Pierre-Simon Laplace in 1805.

·      Albert Einstein's first scientific paper in 1900 was written on the subject of capillarity.

See Capillary Action Yourself

An excellent and easy demonstration of capillary action is done by placing a celery stalk in water.

Color the water with food coloring and observe the progress of the dye up the celery stalk.

The same process may be used to color white carnations.

Trim the bottom of a carnation stem to make sure it can absorb water. Place the flower in dyed water.

The color will migrate via capillary action all the way to the flower petals.

A less dramatic but more familiar example of capillary action is the wicking behavior of a paper towel used to wipe up a spill.

Anne Marie Helmenstine, Ph.D.

Chemistry Expert

Education

Ph.D., Biomedical Sciences, University of Tennessee at Knoxville

B.A., Physics and Mathematics, Hastings College

Introduction

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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