How Can You Make Your Own Rainbow?

Grade range: K-3

Time to complete: 20-30 minutes

Subjects/skills addressed: Science, Math

Objective: Students will create a rainbow with sunlight and water.

Materials needed:

Garden hose with an adjustable nozzle attached

Photographs of naturally occurring rainbows

Picture of a right triangle or angle

Open space outside

Sunshine (the sun should NOT be directly above you) 

Words to know: refract, reflect, angle

Instructions:

1. Show the students images of naturally occurring rainbows (single and double rainbows).

Ask: What colors do you see in the rainbows? How do you think these rainbows are created? Look closely at the double rainbows. How are they different?

2. Show students the picture of a right triangle.

3. Demonstration:

a. Position yourself with the sun directly behind you so that you and your shadow form the legs of a right triangle, as shown.

b. Position the hose approximately halfway between your shadow and you. The actual angle is 42 degrees for the primary rainbow and 50 degrees for the secondary rainbow. However, halfway will be easier for the students to understand.

c. Have a student turn the water on FULL blast. Arc the hose spray to create the rainbow. The rainbow should be formed close to the halfway point between the legs of the triangle.

Ask: What colors do you see in the rainbow? What color is at the top? At the bottom?

4. Have the students take turns creating their own rainbow. It may be possible to create a double rainbow in this manner, but the secondary rainbow will be faint.

Conclusion: To create a rainbow you need a source of light and something that will refract and reflect the light. The light from the sun is refracted (bent) and reflected (bounced) inside the droplets of water from the hose. As each color of the rainbow has a different-sized wavelength, the way they are refracted and reflected causes the sunlight to split into the different stripes of the rainbow.

Create a rainbow in the classroom: In the story, Sometimes Snow Falls in the Summer, a rainbow is created in Ella’s room by a prism. There are many ways to create a rainbow–using CDs, water, water and oil, and many more. Try your own hand at creating rainbows in the classroom.

Where Did The Snow Go?

Grade range: K-2

Time to complete: 45-60 minutes

Subjects/skills addressed: science, math 

Objective: Students will change the density of powdered sugar by adding a liquid. They will use the changed sugar to decorate a snowflake cookie. 

Materials needed:

2 pounds powdered sugar

Milk (2 TBSP per demonstration)

Prebaked sugar cookies

Colored granulated sugar

Vanilla and butter (optional)

Set of measuring cups and spoons

Spoon and spreading knife

Parchment paper 

Words to know: measure, density, more, less 

Instructions:

1. Ask: How do you think snow melts? What happens when it melts?

Explain that when snow melts, the density (how much space it fills) changes. The students will see how this is done by dissolving powdered sugar.

2. Direct a student to fill a measuring cup with powered sugar, making sure that the sugar is not packed into the cup. Level the top with the handle of the spoon.

Ask: Is the cup full of sugar? Let’s see if we can change that.

3. Direct a student to pour 1 teaspoon of milk into the center of the cup of sugar.

Ask: What is happening to the powdered sugar?

3. Direct another student to add a second spoon of milk. A third, etc. Observe what happens to the sugar. Use no more than a total of 6 teaspoons.

Ask: Why does it look like there is less sugar in the cup? Where did it go?

4. Repeat steps 2 and 3.

5. Stir the contents of the cup into a bowl, adding 2 teaspoons of vanilla to flavor.*

6. Use the steps in lesson 2 to create snowflakes that are 1.75″ in diameter from the parchment paper.

7. Cover the cookies with the powdered sugar icing.

8. Place the parchment snowflake on top of the cookie and sprinkle generously with colored sugar, tapping off the extra before removing the snowflake pattern. A clean pin helps remove the parchment snowflakes from the icing. 

Conclusion:

When liquid is added to powdered sugar, the sugar dissolves into the liquid, increasing the density of the sugar. The amount of air between the particles of sugar is reduced, causing the sugar to take up less room in the cup. This is similar to how the density of snow is changed when it melts. The air between the snowflakes is reduced as the snow becomes a liquid.