Make Colorful Carnations
In this experiment, little scientists explore capillary action while making a colorful bouquet of carnations.
Simple explanation: Plants take in water through their stems and deliver it to their branches, leaves, flowers and fruits; this is called "capillary action." The dye in the water lets you see how far the water travels.
More information: Ever wonder how water moves through a plant? There are three forces at work: surface tension and cohesion (forces holding the water together) and adhesion (a force attracting the water to the sides of the stem). Altogether, these forces overcome the downward force of gravity, allowing the water to climb upward through the plant. To demonstrate this, pour a bit of water onto a tray. It will stay together in a puddle -- this is surface tension and cohesion. Now dip a corner of a paper towel into the puddle -- the water will travel up the paper towel; this is adhesion. Altogether, this is capillary action.
Ever wonder what food coloring is? Food coloring is water with tiny bits of solid pigment mixed in. The pigment travels with the water and is eventually left behind in the stem, leaves and flower petals.
Safety Notes
Only a grownup should use a knife or utility scissors to trim the flower stems.
Materials
- plain white carnation - 1+ of this item per student
- utility scissors or knife - grownup only
- clear cup or glass - 1+ of this item per student
- water - enough to fill cup halfway
- food coloring
Instructions
Fill clear cup halfway with water. Be sure the cup will not tip over when you add the flower. Don't overfill the cup because (1) the cup could overflow or get top-heavy, and (2) the extra water will unnecessarily dilute the food coloring.
Add enough food coloring to the water to create a dark color.
Carefully trim the stem of the carnation at a 45 degree angle and quickly place in the water. This will maximize the capillary action.
Allow the flowers to sit for at least 48 hours. Be sure to observe them every few hours. What is happening?
Extensions:
To make two colors on a single flower, split the stem up the middle and place each end in a different color of water.
Substitute stalks of celery, preferably with the leaves still attached, for the carnations.
To make this project a true experiment, measure carefully the water and food coloring placed in each glass and be sure the flowers are the same in size and stem length. Also be sure to place one flower in plain water as a control.
Consider using the same color dye but changing other variables, such as the type of flower (use other white flowers such as roses or daisies), the amount of light or heat the flower receives, the type or position of the cut made in the stem, the length of time between cutting the stem and placing it in water, or an additive such as sugar.
