Capillary Action

Ramisa Maliha

Have you ever noticed how if you dipped the edge of a paper towel in a tray with water, the water rises up the paper towel? The water travels up against gravity! This is due to capillarity or capillary action! Capillarity is the ability of liquids to flow into narrow spaces without any applied force and against external forces such as in this case gravity! Water molecules have a tendency to stick together, so when molecules move up, more follow!

Capillarity allows scientists to carry out chromatography which separates substances according to their ability to move through a stationary phase (eg paper) with the help of a mobile phase (a liquid eg water). Capillarity also allows roots of plants to absorb water up the stem and transport it throughout the plant.

Let us look at two fun experiments to try at home using capillary action!

Chromatography Experiment with Markers

Supplies needed

  1. Markers in a variety of colors

  2. Glasses with water

  3. Paper towels

  4. Scissors

What to do

  1. Cut paper towels into long strips about an inch wide.

  2. Draw a heavy line with a marker near the top of one stripe (black is often a fascinating color that separates into bright blue, green, and yellow).

  3. Hang the paper strip over the edge of the glass of water so that the paper towel touches the water, but the line is above the water.

  4. Watch the color spread as the water travels up the paper.

The incredible thing is when seemingly “boring” colors (like black) separate into many unexpected colors!

Walking Water Rainbow

Supplies needed

  1. 5 wide-mouth glasses or jars

  2. Paper towels (use the kind where you can select a size)

  3. Food dye or liquid watercolors (red, yellow, and blue)

What to do

  1. Take 3 glasses and in the first glass add some diluted red dye or watercolor, in the second blue and in the third yellow.

  2. Arrange the 5 glasses in a row with empty glasses in between the ones with the color as shown.

  3. Take six sheets of paper towels and fold them in half. Place the folded papers on the edge of the glasses so that each end of the paper is in either cup. One end should be touching the dye and the other end in the empty glass.

After a few hours, the dyes would have traveled to the empty glasses and mixed with the colors next to them and create a beautiful mixture!

For more fun experiments and videos you can visit the following links by other youtube channels!

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