Museum of Science, Boston

Books for Kids

  • A Drop of Water
    , by
    Walter Wick
  • Butterflies and Moths
    , by
    Dorling Kindersley
  • EyeWitness Butterfly & Moth
    , by
    Paul Whalley

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Contact the Discovery Center and Living Lab staff at

April 2008: Capillary Action Butterflies

Capillary Action Butterflies

Young children love to explore water! And no wonder- playing in water, with all of it’s interesting properties, presents young children with both satisfaction and challenges.

The Capillary Action Butterflies activity allows children to explore one of water’s most appealing properties: it’s “stickiness”.

Water molecules stick to almost everything- the table, your hand, paper, and even other water molecules. This stickiness is what allows water to move through the coffee filter, taking all of the colors with it and mixing them together.

The Discovery Center’s Capillary Action Butterflies activity encourages visitors develop their observation skills and practice using science tools.

This activity provides a fun introduction to the properties of water, by exploring the scientific concepts of capillary action, adhesion, cohesion, and surface tension.

During the activity, children create a model of a butterfly using coffee filters, markers, water and pipe cleaners. Using this model, grownups are then able talk with children about what a real butterfly is like and how a real butterfly is, and is not, like the model they make.

Creating Capillary Action Butterflies also lets children experience how primary colors mix together to form new colors.

Capillary Action at Home

Continue your Capillary Action explorations at home by

Making Capillary Action Butterflies at Home

Experimenting with Colors & Water

Have each young scientist use the primary-colored markers to color two coffee filters halves.

Help children lay the colored filters flat on a tray or plate and slowly add drops of water with a pipette.

Tip for Grownups: Less is more when it comes to adding water.

When children have finished adding water, help them lay the filters on a paper towel and blot them with a second paper towel. “Finished” happens whenever they like - it’s ok to let some of the filter stay dry.

To create your butterfly:

Pat the coffee filters dry with a paper towel.

Lay the two filter halves side-by-side.

Fold one pipecleaner in half (creating the letter “V” with the pipecleaner).

Pinch filters together at the mid-line.

Slide the two filters into the “V”.

Twist the ends of the pipecleaner, leaving the ends long, to make the body and antennae.

Questions to Think About While You Experiment:

What happens when you drop water on the paper?

Can you see the water moving through the coffee filter?

Look at your butterfly through a hand lens.

What color is a butterfly/?

Can you make an orange -or purple- butterfly?

What is the difference between a moth and a butterfly?

Thinking About What Makes Water 'Sticky'

Capillary action is the result of adhesion, cohesion and surface tension.

Cohesion is the force that holds molecules of water to other molecules of water.

Adhesion is the force that holds water molecules to other materials - like your hand, or paper fibers.

The water molecules at the surface of the water are affected by surface tension - water molecules at the surface cohere to the ones just below more strongly because there are no water molecules above them to cohere to.

In the Capillary Action Butterflies activity, the water molecules at the surface of the water also adhere to the molecules of paper fiber in the coffee filter.

Adhesion of water to the paper fibers in the coffee filter causes an upward force on the water molecules on the edge of a water droplet. At the same time, surface tension holds the surface of the water intact, so instead of just the molecules at the edges moving upward, the whole liquid surface is dragged upward into the air spaces between the paper fibers.

The ‘air spaces’ are the small holes you can see in a coffee filter if you hold it up to the light.