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Rainbow In A Jar

To make this rainbow in a jar, the students are exploring density by layering sugar water to make a rainbow. The materials are all things you most likely already have on hand.

You Will Need:

Approx. 2 cups of warm tap water

1/2 cup measuring cup

1 Tablespoon measuring spoon

4 small jars of glasses

Approx. 1 1/2 cups of granulated white sugar

Red, blue, yellow and green food coloring

Tall thin glass or test tube. I used an old Starbucks bottle


4 popsicle sticks


Step 1: Measure a 1/2 cup of warm tap water into the 4 jars.

Step 2: Add 2 drops of food coloring to each of the 4 jars.

Step 3: To the jar of red water, add 2 tablespoons of sugar. To the jar of yellow, add 4 tablespoons of sugar. To the jar of green water, add 6 tablespoons of sugar. To the jar of blue water, add 8 tablespoons of sugar.

Step 4: Stir each of the jars to dissolve the sugar. If your water is not warm enough to dissolve the sugar, put the jar in the microwave for 30 seconds at a time, stirring in between until the sugar is dissolved.

The children can already see at this point that by dissolving increasing amounts of sugar, you’re increasing the density of the sugar water solutions. They can easily see that the jars all started the same and now the blue looks a lot fuller than the red.

Step 5: Pour about an inch of the blue water into the bottom of your glass or test tube.

Step 6: Use your straw to gently drip the green water on top of the blue layer. It works best to place the straw to the side of the glass just above the blue layer. You want to add the layers to the glass slowly and carefully, otherwise they’ll mix together resulting in a muddled rainbow.

Step 7: Add the yellow layer next using the same method and last the red layer. Stand back and admire your beautiful rainbow!

I hope your children love making the rainbow and learning about density in a fun way!

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