Color-Changing Flowers

Have you ever seen bright green flowers around St. Patrick’s Day? In this project, you’ll get to dye some yourself and also learn a little about how flowers live in the process.

What You Need:

  • fresh white carnations, mums, or other all-white flowers
  • green food coloring
  • jar or vase of water

What You Do:

  1. Add at least 15-20 drops of food coloring to the container of water and mix it well. The more coloring you add to your water, the more the color will show up in your flowers, so make sure you use plenty!

    transpiration to dye flowers

  2. Cut about a half inch off the end of each flower’s stem at an angle. Making a fresh cut at an angle will allow the flowers to absorb more water.

    transpiration to dye flowers

  3. Place the flower stems into the colored water and observe how the petals look. They are pure white, right?
  4. After about an hour, check on the flowers. Have the petals changed at all?
  5. Leave the flowers alone for several more hours and check on them periodically. After a full 24 hours, the petals should have quite a bit of green on them.

    transpiration to dye flowers

What Happened:

You probably know that plants “drink” water from soil through their roots, and it in turn travels up the plant’s stem or trunk (in the case of a tree) and to its leaves, flowers, or fruit. This process is called transpiration and it helps plants cool off. When a flower’s stem is cut off of the plant it grew on, the stem is still able to suck water up to keep the flower alive for a little longer, even though it no longer has roots attached to it.

How does that happen? Well, it works sort of like sucking on a straw to get a drink from your glass to your mouth. When water in the flower’s petals and leaves evaporates, it pulls more water up the stem to replace the water that evaporated. How does the evaporating water pull more water up with it? Water has a special property, called cohesion, that causes it to stick to itself. Water moves through tiny tubes in the stem called xylem (say ZYE-lum). Because of cohesion, each drop of water pulls another drop along behind it, effectively moving water up the stem and into the flower.

Adding green dye to the water allowed us to see how water travels from the flower's roots, up its stem, and then transpires (or evaporates) at its petals. As a bonus, you get pretty green flowers you can use as decoration for St. Patrick’s Day!

When you’re done enjoying your colored flowers, ask an adult to slice upwards through the stem of one to see the tiny tubes full of green dye and how the colored water traveled up the stem to change the color of the flower’s petals.

Make A Rainbow

What You Need:

  • a clear square or rectangular baking dish
  • a handheld mirror
  • water
  • a flashlight (with a normal bulb rather than an LED)
  • a white wall or sheet of paper
  • sticky-tack or modeling clay

What You Do:

  1. Fill the baking dish about two-thirds full with water.
  2. Carefully set the mirror in the bottom at an angle. You may find it helpful to use a small piece of modeling clay or sticky tack to hold it in place.
  3. Position the pan and mirror so that the mirror reflects toward a white wall. (Or ask a helper to hold a sheet of white paper about six inches from the mirror.)
  4. Turn off the lights in the room. Turn on your flashlight and shine it through the water directly at the mirror.

    refraction rainbow

  5. Can you find the rainbow on the wall or sheet of paper? You may need to adjust the angle of your flashlight or the mirror to get it to appear brightly.

    refraction rainbow

What Happened:

How did the pan of water with a mirror in it make a rainbow on your wall? The water in the dish caused the beam of light from your flashlight to bend. This is called refraction. When white light (like the kind from a flashlight’s bulb) refracts, all of the colors it is made up of become visible! You couldn’t see the different colors until they hit the mirror and were reflected back out of the water as a rainbow! Note that the rainbow may not have had a bow shape like ones you would see in the sky. That’s because a natural rainbow in the sky is actually a full circle, but unless you are above the rainbow, you can only see half of it.

Something similar sometimes happens after a thunderstorm; but instead of the water being in a dish and a flashlight making the light, the water is in the form of droplets in the air (often in clouds) and the light comes from the sun! Beams of sunlight hit drops of water in the sky and are refracted (separated into their colors) and reflected back out, allowing us to see a rainbow if we’re at the right angle.

Science Lessons

White light, like the kind from a flashlight, is actually made up of seven different colors! Rainbows are formed when light refracts, or breaks apart into its separate colors. Do you know the colors of a rainbow? The colors of a rainbow are always in the same order. You can remember them by saying the name “Roy G. Biv,” which stands for red, orange, yellow, green, blue, indigo, and violet. Here's how refraction works to make a rainbow in the sky:
You can see a rainbow when the sun is low in the sky behind you and there is rain off in the distance in front of you. Beams of light from the sun shine towards the rain in the air and when the light goes into the raindrops, it is bent (refracted). When the light bends, it breaks into all of its colors (the colors of the rainbow). When the light hits the back of the raindrop, it is reflected and bounces back in the opposite direction (back towards you). Each color leaves the raindrop at its own angle, different from all the others. The colors of light bounce back to your eyes and form a half-circle shape, because of their different angles, and you see a rainbow of all the colors!

The colors of the rainbow always appear in the same order because each color always bends at the same angle. The red angle is reflected into your eye at the top, violet at the bottom, and the others at their specific place in between.

Have you ever heard that there is a pot of gold at the end of a rainbow? Since a rainbow is a visual reflection of light rather than a physical object, you can never really get to the end of one. As you begin to move towards it, the rainbow will move with you and will eventually disappear altogether. (Remember how the angle of the sunlight and raindrops combine in order for you to see a rainbow? When that is thrown off, you will no longer be able to see the rainbow!)

Gold is a pure element that occurs naturally in various places on Earth. Gold is the only metal that naturally has a yellowish color – other elements only take on a yellow color after reacting with different substances. Even though it is a heavy substance, it is very malleable, which means it can be stretched and formed into other shapes fairly easily. In fact, because it is so malleable, pure gold can be pounded into a very thin sheet or stretched into a thin wire or thread! Besides having a high value as money, gold is used to make many things, from jewelry to medals and awards to decorations.

Science Words

Refraction—when light bends because it passes through a different material like when it goes from air into glass or water.
Reflection—when light hits an object and bounces back in the opposite direction. A reflection could also mean an image, such as a reflection of yourself in a mirror or a puddle of water.