So it’s Thanksgiving, and what do we find at the bottom of our crisper drawer, but a bunch of wilted celery. Now I suppose I could chop it up and add it to the stuffing, but I think to myself it’s a great time for a little kitchen experiment instead — a perfect opportunity to learn about capillary action with my kids.
What is capillary action?
Capillary action, or capillarity, is the moving of water using forces of adhesion, cohesion, and surface tension. Think of plants and trees which suck up water. Or a paper towel placed in a glass of water.
To see firsthand what is going on with this process, you can do a little experiment with the old celery lying at the bottom of your crisper drawer.
First, take your celery and cut off the bottom one inch of the celery stock.
Get three glasses and fill them halfway with water along with 10 drops of food coloring.
Place your stalks of celery into a glass and wait. Within a few hours you will notice that the leaves have started changing color.
So what’s happening here?
Within the stalks of celery there are tiny vertical tubes. This vascular tissue in plants is called xylem. These tiny tubes draw up water using capillary action. Basically, because water is inherently “sticky,” it clings to the inside of the tube or column inside of the celery, drawing itself up, and, in the process, seemingly defying gravity. So it’s normal for us to say the plant is “drinking” water, but really the water is pulling itself up through the plant.
I asked my kids to predict how long they thought it would take for the celery to absorb the water. Both said they thought it would take several days, but within a few hours we saw evidence of the water’s travel.
The food coloring allowed us to follow the water’s path up the celery stalk and through the veins in the leaves.
Our takeaway from this project: Science is cool.