Let's Make A Rainbow!
Although this is the first year we are formally homeschooling some of our kids, we've been doing little experiments like this one for a long time now. I saw this one a while back and knew that it would have to be something we attempted. It is fun to watch the process unfold, and although I thought only the younger homeschoolers would be interested, my middle and high school kids were still checking the jars for changes.
|This is after sitting about 6 hours. |
Initially, there will be no orange, green or purple
and all the paper towels will be white.
- 6 clear glass or plastic containers that are the same size
- Red, Yellow and Blue food coloring
- 2 paper towels, cut into three strips each, for a total of 6 strips
- large baking sheet (optional)
To begin, you want to fill your containers roughly 1/2-2/3 of the way full of water. Put the jars somewhere that they won't be disturbed for about 24 hours, or alternatively, place them onto a large baking sheet so that you can move them easily. Arrange the jars in a circle, sides touching with the center open.
Place several drops of red food coloring into one jar and stir. Skip the second jar, leaving it plain water. Add several drops of yellow food coloring into the third jar and stir. Skip the fourth jar. Add several drops of blue food coloring to the fifth jar and stir. Leave the last jar plain water as well.
At this point, you have 6 jars, 3 with the colors added, 3 plain water.
Take the strips you've cut from the paper towels and fold each strip lengthwise three times, smoothing the edges. Place one end in the red jar, the other in the clear jar beside it. Repeat this until there is a paper towel strip connecting all the jars to the ones beside them. Note that none of the colors are touching each other. If you are doing this as a lesson plan, ask the students what they think will happen. Make predictions and ask them what they are basing those predictions on.
Leave the jars alone. The colors will begin traveling up the paper towels and into the adjacent jars within a few hours. The fuller the jars are, the quicker the process will be. By 18-24 hours, the colors will have transferred and you will have created a rainbow with 6 vivid colors.
What does this project teach?
- Primary and secondary colors - Red, blue and yellow are primary colors in the spectrum. Mixing them together creates the secondary colors: orange, green and purple.
- Properties of water - Water is a tremendously stable molecule, one that does just about everything possible to stay together - so when water begins to travel up the paper towels, it keeps taking more and more water with it. In fancy science terms, this phenomenon can be explained by adhesion and cohesion.
- Cohesion: water is attracted to water and bonds to water easily
- This causes the water to travel together into the other containers. Notice that the levels of water in the jars remains constant, as water is actually moving back and forth between and among all the jars at the same rate.
- Adhesion: water is attracted to other substances
- Capillary action is when the water becomes attracted to the jar itself and the paper towel, and begins to move up the towel.
- There are some great videos about the properties of water available to watch. Here is one I highly recommend from Khan Academy. Though some of the terms in this video probably would place it at a middle school level, my 7 year old understood most of it as well.
- This is a great resource for even more details about the science involved in this project if you have a kid who needs to know everything about it!