Today we’re going to talk about absorption! What does it mean to absorb? Absorption occurs when one substance takes in another. We’ve done some other activities involving absorption in the past, such as when we did our rainbow inchworm (http://www.discoveryexpresskids.com/blog/rainbow-inchworm) and candy chromatography (http://www.discoveryexpresskids.com/blog/candy-chromatography).
Let’s look at an example of absorption.
* Sponge
* Water
* Tablespoon
Here’s what to do!
1. Have you ever used a sponge? What does a sponge do when it runs into liquid?
2. Fill a tablespoon with water and dump it onto the sponge. What happens to the water?
3. Wring out the sponge into the sink.
4. Check how many tablespoons of water the sponge will hold. Dump one tablespoon of water at a time onto the center of the sponge until the water starts to seep out. At this point, the sponge is fully saturated. This means that the sponge will hold no more water. Why do you think a sponge absorbs water so well? What other materials absorb water? What materials might not absorb water?
For other activities involving saturation, check out http://www.discoveryexpresskids.com/blog/sweet-solutions-rock-candy and http://www.discoveryexpresskids.com/blog/floating-egg.
Now that you understand what absorption means, let’s test out some different materials. You are going to use watercolor paints on different surfaces to see how well they absorb the paint.
Watercolor Absorption
* Paper towel
* Cardboard
* Paper plate
* Styrofoam plate
* Wood
* Tissue paper
* Facial tissue
* Wax paper
* Liquid watercolor paints
* Cup of water
* Paint brush
Here’s what to do!
1. Cover your work space with newspaper or a disposable tablecloth.
2. Place all your materials on your work space.
3. Fill a cup with water to rinse your paint brush out.
4. Start painting! Pick one material to start with and paint on it. Stop and observe before you move on to the next one. How well did that material absorb the paint? How can you tell that the material is absorbing the paint at all? Clue: Think back to the sponge example.
5. Move on to the next material. Paint on it and observe!
6. Keep on painting and record your findings. Which materials absorbed paint the best? Which materials absorbed paint the least or even resisted the paint (that is, the paint pooled on the surface, or formed small beads of liquid)? You may have seen the paint bead on the surface of some materials and not even absorb at all. Why do you think some materials absorb better than others?
Let’s try another absorption project that you can keep! The chromatography activities that we’ve done in the past are similar to what we are going to do today. In this activity, you will see how marker ink on paper towel travels when you soak the paper towel in water.
If you’ve done one of our chromatography activities in the past, you’ll remember that the reason water can travel up a paper towel, seemingly defying gravity, is because of capillary action. 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.
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.
Grow your own rainbow
* Paper towel
* Markers
* Plastic container
* Water
Here’s what to do!
1. In the top left corner of your paper towel, place a large dot of red marker. Your dot should be at least one inch wide.
2. Leave a little space to the right of the red dot and draw an orange dot. Continue on until you have drawn dots for every color of the rainbow.
3. Fill your plastic container with about half an inch of water.
4. Place your paper towel, colored side down, in the plastic container so that only the very bottom touches the water. Drape the top of the towel over the side of the container.
5. Watch what happens! The paper towel quickly absorbs the water, but what happens to the marker dots? You should see the color slowly spreading as the water climbs up the paper towel. As the water travels, the ink from the marker dots travel with it! Do some colors travel faster than others?
6. Wait a few minutes, and voila! You just grew a rainbow!
Extension: Have a color race! See if some colors of ink really do travel faster. Which color reached the top the fastest? Slowest? Try creating different designs and make more chromatography art!
References
http://www.learnplayimagine.com/2014/02/combining-art-and-science.html
http://weirdsciencekids.com/DefinitionAbsorption.html
http://teachbesideme.com/rainbow-science-absorption/