Week 2: Colors
(Click here to download the supplies and activities list)
Source: Steve Spangler Science Website
1. Mixing Colors
a. Color Wheel
A color wheel shows the relationship between the colors.
The three primary colors (red, yellow, and blue) cannot be made by mixing two other colors. On the color wheel below, the primary colors are located on the points of the main triangle. Use colored markers to fill them in.
The three secondary colors (orange, green, and violet) are each a mixture of two primary colors. On the color wheel, the secondary colors are located on the points of the upside-down triangle, between the colors they are made from. Again, use colored markers the color in the secondary colors.
b. Color mixing
How fast can you mix 24 different colors using only red, yellow and blue?
Materials you will need (you can order these at SteveSpanglerScience.com):
* 1 Mini-mixing tray
* 3 small Plastic cups.
* True Colors Color Mixing Tablets (Red, Yellow and Blue)
* 1 or more Pipettes
Experiment:
- Fill the three plastic cups 3/4 full with warm water.
- Open the package of coloring tables and place a different colored tablet in each cup. You only need one tablet per cup.
- Find the three pipettes - plastic eye-droppers of sorts. Dip the end of the pipette into the colored water, squeeze the bulb to push the air out, and release your squeeze to draw up some liquid. 4. Pick one of the 24 little wells and add a little squirt of blue liquid followed by some yellow. Voila! You made green! Don't stop there. Keep mixing colors... a few drops of this and that to make as many different colors as possible.
- Carefully pick up the Mini-Mixing Tray and hold it up to the light to gaze at the rainbow of colors you've created.
2. Separating Colors
Is
Black Really Black? Let’s see... black is black!!! Well, maybe not.
There is literally a rainbow of color hiding in just one black dot!
Materials you will need:
- a strip of paper towel (write your name at one end of the strip with a sharpie)
- Clean bowl filled with water
- Black pens of different brands (water soluble)
Experiment:
- Start by using a black pen (not the sharpie) to draw a thick line across a strip of paper towel, about 1-2 inches from the end (not the end where you wrote your name).
- Dip the end of the paper with the line into the bowl. Be careful, do not get the line wet, only the very tip of the paper should be in the water. As the paper gets wet, the water will slowly crawl up to the paper and start to get it wet, too. This may take a while, so be patient. It’s worth the wait!
Observations
What happens to the black dots when they get wet? How did the colors get on the paper? Take the paper and the pipe cleaner off the cup of water when the “design” is about half the size of the paper. If you let the paper soak up too much water, the design gets blurry and faded. Set your paper some place safe to dry.
How does it work?
So, is black really just black? No! Black is a whole bunch of colors
mixed together. There’s literally a rainbow of color hiding in just one
black dot! The burst of color that you see on the filter paper proves
that black is really a combination of colors. This technique of color
separation is actually called chromatography, which was originally used
to separate different plant pigments. The science behind the rainbow is
simply this: The ink dissolves in the water (that’s why they call it
water soluble) and moves in between the fibers of the paper where it is
separated into bands of color. As the water travels up the paper, it
carries the pigments along with it. Different-colored pigments are
carried along at different rates; some travel farther and faster than
others. How fast each pigment travels depends on the size of the
pigment molecule and on how strongly the pigment is attracted to the
paper. Since the water carries the different pigments at different
rates, the black ink separates to reveal the colors that were mixed to
make it. You might see as many as six or seven different circles of
color.
Try this... Experiment with other black pens found around
the house. You’ll want to make sure the pens are water soluble to get
them to separate into individual colors. As you experiment with
different brands of pens and markers, you’ll notice that each brand
leaves its own unique color pattern on the filter.
3. Pretty Science
You can also make really good looking clothes with science. Here is an alternative to Tie Dye.
Materials you will need:
- pre-washed, plain white t-shirt material (you can color a whole t-shirt if you want) - washing the material ahead of time removes the starch.
- sturdy plastic cups.
- different colored sharpies.
- rubber band.
- eye dropper.
- rubbing alcohol.
Experiment:
- Place the cup under the material (or inside the shirt if you are using a whole t-shirt). Stretch the rubber band over the t-shirt and the cup to secure the shirt in place.
- Place about 6 dots of ink from one marker in a circle pattern about the size of a quarter in the center of the stretched out fabric. If you like, use another color marker to fill in spaces in the between the dots. There should be a quarter size circle of dots in the middle of the plastic cup opening when you are finished.
- Slowly squeeze approximately 20 drops of rubbing alcohol into the center of the circle of dots. Apply as much or as little rubbing alcohol as desired, but do not let the pattern spread beyond the edges of the cup.
- Allow the developed design to dry for 5 mnutes before moving on to a new area of the shirt. To set the colors place the material in the dryer for 15 minutes.
Observations
As the rubbing alcohol absorbs into the fabric, the ink spread in a circular pattern expanding outward from the center. The result is a beautiful flower-like pattern, however, students often remark that the design looks like the colorful surface of a compact disc.
How does it work?
This is really a lesson in the concepts of solubility, color mixing, and the movement of molecules. The sharpie markers contain permanent ink which will not wash away in water (that is why we do not use black sharpies for the "separating colors" experiment). However, the molecules of ink are soluble in anther solvent called rubbing alcohol. This solvent carries the different colors of ink with it as it spreads in a circular pattern from the center of the material.
4. Color changing milk
It's
an EXPLOSION of color! Some very unusual things happen when you mix a
little milk, food coloring, and a drop of liquid soap. Use the
experiment to amaze your friends and uncover the scientific secrets of
soap.
Materials you will need:
* Milk (whole or 2%)
* Dinner plate – or metal pie pan
* Food coloring (red, yellow, green, blue)
* Dish-washing soap (Dawn brand works well) in a small cup
* Cotton swabs
Experiment:
- Pour enough milk in the dinner plate to completely cover the bottom and allow it to settle.
- Add one drop of each of the four colors of food coloring - red, yellow, blue, and green - to the milk. Keep the drops close together in the center of the plate of milk.
- Find a clean cotton swab for the next part of the experiment. Predict what will happen when you touch the tip of the cotton swab to the center of the milk. It's important not to stir the mix just touch it with the tip of the cotton swab.
- Place a drop of liquid dish soap (the Dawn brand works well) on the tip of the cotton swab. Place the soapy end of the cotton swab back in the middle of the milk and hold it there for 10 to 15 seconds. Look at that burst of color! It's like the 4th of July in a bowl of milk: mini-explosions of color.
- Add another drop of soap to the tip to the cotton swab and try it again. Experiment with placing the cotton swab at different places in the milk. Notice that the colors in the milk continue to move even when the cotton swab is removed. What makes the food coloring in the milk move?
How does it work?
Milk
is mostly water but it also contains vitamins, minerals, proteins, and
tiny droplets of fat suspended in solution. Fats and proteins are
sensitive to changes in the surrounding solution (the milk).
When
you add soap, the weak chemical bonds that hold the proteins in
solution are altered. It's a free for all! The molecules of protein and
fat bend, roll, twist, and contort in all directions. The food color
molecules are bumped and shoved everywhere, providing an easy way to
observe all the invisible activity. At the same time, soap molecules
combine to form a micelle, or cluster of soap molecules. These micelles
distribute the fat in the milk.
This rapidly mixing fat and soap
causes swirling and churning where a micelle meets a fat droplet. When
there are micelles and fat droplets everywhere the motion stops, but
not until after you've enjoyed the show!
There's another reason the
colors explode the way they do. Since milk is mostly water, it has
surface tension like water. The drops of food coloring floating on the
surface tend to stay put. Liquid soap wrecks the surface tension by
breaking the cohesive bonds between water molecules and allowing the
colors to zing throughout the milk. What a party!
Repeat the
experiment using water in place of milk. Will you get the same eruption
of color? Why or why not? What kind of milk produces the best swirling
of color: skim, 1%, 2%, or whole milk? Why?
Additional Info:
Detergent, because of its bipolar characteristics (hydrophilic on one
end and hydrophobic on the other), weakens the milk's bonds by
attaching to its fat molecules. The detergent's hydrophilic end
dissolves in water and its water-fearing end attaches to a fat globule
in the milk.