Fun with Science

How Does a Paper Towel Absorb Water?

Have you ever wondered just exactly how a paper towel absorbs water? Let's investigate.

What you'll need:

  • paper towels
  • water
  • saucer or shallow bowl
  • food coloring
1. First, put some water into a saucer or shallow bowl.

2. Add a drop or two of food coloring and stir until dissolved.

3. Dip the corner of a paper towel into the colored water and watch what happens.

Did you notice that the colored water begins to spread upward and away from the corner of the paper?

How does the water actually move up through the paper towel? It happens due to a force of attraction between the paper fibers and the water. This force is called capillary action. The water is pulled up into the open spaces between the fibers in the paper, soaking the paper as it absorbs the water. When the weight of the water in the paper is equal to the upward attraction, then the water stops rising.

Capillary action is also the force by which plants draw up water through their roots, and by which sap rises in trees in the spring.

Adapted from Is Science Magic?, by Ovid K. Wong (Childrens Press, Chicago, 1989).

 

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