Today, you will learn about absorption, capillary action, and mixing colors!
We've done other experiments involving capillary action and absorption in the past, such as when you tried paper and leaf chromatography (http://discoveryexpress.weebly.com/blog/is-a-black-marker-really-just-black-is-a-green-leaf-really-only-green-these-are-the-questions-well-answer-today-using-chromatography) or when you tried candy chromatography (http://discoveryexpress.weebly.com/blog/candy-chromatography).
Today, you will be doing something similar, but instead of putting marker directly on paper towel, you'll be soaking the paper towel in colored water and watching that water travel from one cup to another via the paper towel in between the cups. The reason that the water can travel up a paper towel, seemingly defying gravity, is because of capillary action.
How does capillary action work? Capillary Action is what causes the water to “climb” up your paper. Because of cohesion within liquid molecules, and adhesion between the liquid and the solid, capillary action allows liquids to move against the forces of gravity.
Remember, cohesion means the molecules like to stick together. Adhesion means that the molecules like to stick to other things. In this case, the water molecules like to stick to the paper towel.
Check out this link for more information: http://water.usgs.gov/edu/capillaryaction.html
In our chromatography activities, we were separating colors into their component colors. For example, you found out that a black marker is actually made up of several different colors. In this activity, instead of separating colors, you’ll be combining them. The end result will look like a rainbow inchworm!
The colors you are starting with are red, blue, and yellow. These are called primary colors. How do you get other colors? Take a look at the color wheel below. When you combine certain primary colors, you get secondary colors, such as purple, orange, and green. When your red, yellow, and blue mix in the activity below, you will see those colors combine to create new ones!
YOU WILL NEED:
- 7 clear cups
- Paper towel
- Food coloring
- Old newspaper (to cover your work station)
Here's what to do!
1. Line up the 7 cups so they are right next to each other.
2. Add water to the 1st, 3rd, 5th, and 7th cups. Leave the cups in between (2, 4, and 6) empty. Cups 1 and 7 should be about half full. Cups 3 and 5 should be about 3/4 full.
3. Add three drops of red food coloring to the 1st cup and the 7th cup.
4. Add three drops of yellow food coloring to the 3rd cup and three drops of blue food coloring to the 5th cup. Cups 2, 4, and 6 should still be empty.
5. Fold one paper towel in half, crease it, then fold it in half again the long way, or "hot-dog style."
6. You should now have a paper towel strip that's a few inches wide. Fold that strip in half again "hamburger style," and crease the fold. When folded, the strip should be about as tall as the cups you are using. If the paper towel is too tall, cut a little bit off the bottom.
7. Place one end of the paper towel strip in cup 1 (with the red water) and the other end in cup 2 (empty).
8. What happens when the paper towel strip touches the red water? You should see the paper towel strip absorbing the red water as the red water climbs up the paper towel strip. How is the water defying gravity?! Remember what we learned about capillary action!
9. Repeat steps 5-6. Place one end in cup 2 and the other end in cup 3.
10. Repeat steps 5-6. Place one end in cup 3 and the other end in cup 4. Continue this until you have paper towels leading all the way to cup 7.
11. Take a look at your work. There should be paper towels zig-zagging from cup 1 to cup 7. What do you notice is happening to the paper towels? What's happening with the colored water? What do you think will happen to the empty cups? Take a moment to write down your predictions.
12. Now all you have to do is wait! Write down your observations as you watch the water travel. Check back in a few hours.
13. What happened to the water? It should have traveled from the full cups to the empty ones until there was about an equal amount of water in each cup. What do you notice about the colors in cups 2, 4, and 6? They're a combination of your original colors! The two cups on either side helped create new colors in your previously empty cups.
Extension: Can you think of a way to extend this activity? How could you add more colors or shades to your Rainbow Inchworm?