Capillary Action Satisfaction

Due to a recent family tragedy there have been lots of flowers and plants at our house. The awesome thing about kiddies is that everything is a source of curiosity for them. While I’ve fielded many questions about death, I’ve gotten probably as many questions about the flowers. Those are much more fun to answer.

Question: “Mommy, if gravity makes everything go down and we put the water in the bottom of the vase, does the flower part at the top never need any water?”

Answer: “Actually, the flower gets water too. Water can defy gravity… Defy? Oh, that means that water can choose not pay attention to gravity. Water can defy gravity if it has a root or something to travel up on. That’s called capillary action.”

I stop to set up a very easy and fun experiment.

Experiment 1-

Step 1: Gather supplies. Get clear cups, bath fizzies, and paper towels. I used tiny tubs that we bought for peanut butter, but use mostly for science experiments and spa days, because I don’t want to clean up the mess later. With disposable cups I can throw everything away when we are done.

Step 2: Set up the cups. Put bath fizzies in every other cup in a circle. To make a pretty rainbow put a red fizzie, skip one, yellow fizzie, skip one, then blue fizzie, skip one.

Step 3: Add the paper and water, and watch the fun. Twist six paper towels (we used three cut in half because our cups are so small) and use each one to connect two adjacent cups. In the end you will have a circle of paper going in and out of the cups (see pic below). Add water only to the cups with fizzies in them.

We watch as quite quickly the paper towels suck up the water in the red, blue, and yellow cups. Not a big surprise. But when the saturated paper towels start depositing water into the empty cups the kiddies stop talking and watch in amazement.

  

In just a few minutes we have a full rainbow and no empty cups. In fact, the level of water is about the same across all cups.

Then we talk some more about capillary action while I pull some new supplies (six more small cups, two larger cups, leafy greens with stalks, and fingerling potatoes).

Capillary action can defy gravity because of the fact that water molecules stick together (a term called cohesion, but I didn’t add that term to the kiddies vocabulary today so that we can focus on capillary action). Water molecules also stick to other things (adhesion, another vocab word we skipped for now so as to not overly confuse things). The water, stuck to itself and the paper towels, is stronger than gravity so it keeps climbing up until the pull of gravity is too strong for it to go any higher.

You can see it well with potatoes. Watch.

Experiment 2-

Put water and bath fizzies in cups. Slice the fingerling potatoes in half. Watch as the colored water climbs up the potatoes. Note, use darker, more saturated colors. The lighter colors we use didn’t show up very well.

This one you have to wait for. The picture is from 15 minutes later. We leave it out for a couple of hours, and I point out how the water never gets to the top of the potatoes because eventually gravity is too strong for the water to keep climbing.

Big shout out to my babysitter who cleaned up the mess we left behind!! Science, not time management, is my thing ;)

Experiment 3-

While we wait for experiment 2, we move on to experiment 3. A real plant. Put water and a fizzy into a cup, and put a leafy or flowered plant in the cup. Ideally we’d have used a plant with roots.

Abigail made my day because when she dropped her fizzies in, and I asked the girls who knew what was making them fizz, Abby answered, “Carbon dioxide coming out!” That’s my girl!

It’s hard to see in the pictures, but the white parts of the leaves started to turn blue (hours, and an outfit change, later) as the plant drinks up the water. If you have white flowers, like daisies or roses, the flowers will turn a pretty new color, which is a good additional experiment.

I tell the kids that we see capillary action every day in more than just plants. 
-The hairs of a paintbrush are able to suck up the liquid paint and hold it. When the brush gets full, or when you push hard, the brush drops the paint onto the paper.
-Paper towels use capillary action to clean up messes.
-Daddy’s workout shirt says it is a wicking shirt that sucks the sweat off of Daddy while he works out. That is capillary action in action.
-Pens use capillary action to draw ink to the tip from the reservoir at the bottom, though we help by turning the pen upside down.

The kids may be getting saturated on other examples of capillary action, but I have one more.

Did you know that we have capillaries in our bodies that carry blood?

Briana says, “No, then all of our blood would be in our head, and I know that if you cut your finger it bleeds.”

Abigail says, “That’s because gravity makes the blood go back down.”

“Then it would all be in our feet and you’re still wrong.”

Our little debate is taking a turn away from friendly, so I offer a solution.

“Actually we have a heart that helps pump the blood up, down, and sideways throughout our bodies.”

**

The next morning after church, I sit down to write this blog entry and Briana sees the pictures and asks me what would happen if we used different size paper in our experiment.

“Well,” I tell her, “that’s the difference between a big plant with thick roots and a smaller one with thin roots. Go get your bath tabs and we can see what would happen.”

So we set up again. This time as a race. At the finish line, another fizzy to ignite.

Ideally we would have measured the paper towels to make sure that our strips are the same size. Briana used the short end of the paper towel to make her skinny strips, and Abby used the long side to make her fat ones. Oh well. Everyone was too excited to see the race and didn’t want to fix it and that was okay by me.

Skinny is off to a good lead, though we all notice that the fat one is carrying more water into the center cup when it gets there. In fact, that line's starting cup runs completely out of water and we have to add more - twice.

Ignition! We have a winner - the skinny one! It was exciting that when the water hit the last cup it set off the bath fizzie.

We also talked about how the color dissipated as it travelled down the paper towel. Eventually all three lines ignite.

“Would you want a fat root or a skinny root if you were plants?” I ask the kiddies. 

“Well,” says Abigail, “with a skinny root you get your food faster, but with a fat root you get more food. I want more food.”

Both kiddies want fat roots for a while but after realizing that eventually all of the roots get roughly an equal amount of food, they decide that a medium root might give the best of both worlds.

I’m glad to see the knowledge seeping in and mixing with their critical thinking.

<3 Pedigreed Housewife