# Water colors: can you change the color of light that is in water?

THINK: What color is seawater? How would seawater look different if you were to add mud to it?

PREDICT: Light (white light, or sunlight) is made of seven colors: red, orange, yellow, green, blue, indigo, and violet. When light passes through a substance, some of these colors get absorbed (soaked up) by the substance, while others pass through. The colors that pass through are the colors you see. Would you expect the color of light shining through water to change if you were to add milk to it? What color do you think the light would be?

```You'll Need

* A clear plastic cup
(9 ounces or larger)

* Water

* Flashlight

* Milk

* Teaspoon

Procedure:

1. Fill a clear plastic cup slightly more than halfway
with water.

2. Turn the lights in the room off.

3. Hold up the cup so that one side of the cup is facing
you. Then, place the flashlight at the opposite side of
the cup.

4. Turn on the flashlight and shine it straight through
the cup of water. The light should be shining toward
you. Observe the color of the light as it passes
through the cup of water.

5. Turn the lights in the room on.

6. Next, add 1 teaspoon of milk to the water in the
cup. Use the teaspoon to stir the milk and water.

7. Repeat Steps 2 through 4.

8. Compare the color of the light you saw in Step 7 to
the color of the light you saw in Step 4.
```

[ILLUSTRATIONS OMITTED]

Conclusions

1. How did the color of the light change after you added milk to the water?

2. The colors of the light you saw in the milk-and-water mixture were able to pass through the mixture. Which colors of the light did not pass through but were absorbed?

3. Given your findings, why do you think the sea looks green instead of blue in some places?

WATER COLORS

SCIENCE CONTENT STANDARD

* Abilities necessary to do scientific inquiry

* Properties of light For Grades 5-8

* Abilities necessary to do scientific inquiry

* Interactions of light and matter

Life Skills--Following directions

Estimated Time: 25 minutes

Discussion Questions

* What are some liquids that you can't see through? (Possible answers: milk; hot chocolate)

* Do you think light is able to pass through liquids that you can't see through? (Possible answer: Yes, but only certain colors of file light are visible.)

AFTER EXPERIMENTING

Conclusions:

1. When the light passed through water, it appeared white. But as the light passed through the milk-and-water mixture, it appeared orange.

2. The colors of light that were absorbed were: yellow, red, blue, green, and violet.

3. Particles in the water--such as seaweed or algae--make the sea look green in some areas.

RESOURCES

* www.webexhibits.org/causesofcolor/This site delves into different sources of light and explains why certain objects appear to be a certain color.

* Magic School Bus Chapter Book #I 9: Color Day Relay by Gail Herman (Scholastic, 2004) takes the reader on an adventure with Miss Frizzle and the gang. The book is packed with lessons on light and color.