Capillary Action
Capillary action is the way water travels upward through narrow spaces on its own, like when a paper towel soaks up a spill.
Stand a paper towel upright in a shallow dish of colored water. The water climbs up the towel on its own, without anyone pushing it. Tiny gaps between the towel fibers pull the water upward, like a chain of hands passing a bucket from one to the next. The narrower the gaps, the higher the water climbs.
Explaining capillary action by grade level
When you dip a paper towel into water with dissolved candy colors, watch what happens. The water climbs up the paper all by itself. It moves through tiny gaps in the paper, pulling the colors along with it. The water holds onto the paper and pulls itself higher, one tiny step at a time.
Projects that explore capillary action
Water moves through tight spaces on its own. Place a coated candy on a circle of filter paper and drip water onto it one drop at a time. The water dissolves the coating and spreads outward through the paper, carrying different inks with it. Because each ink travels at a different speed, rings of separated color appear around the candy after a few minutes. Some candies reveal two or three hidden inks — try several colors to see which contains the most.
Water sticks to paper fibers and pulls more along. You set up seven cups in a row. Red, yellow, and blue water travels up the paper towels and mixes new colors.