I love incorporating easy science experiments into the classroom as often as I can. I thought this rainbow in a jar science experiment was perfect for March.
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.
THIS ACTIVITY WORKS WELL WITH
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
Measure a 1/2 cup of warm tap water into the 4 jars.
Add 2 drops of food coloring to each of the 4 jars.
To the jar of red water, add 2 tablespoons of sugar. To the jar of yellow, add 4 tablespoons of sugar. In the jar of green water, add 6 tablespoons of sugar. And to the jar of blue water, add 8 tablespoons of sugar.
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 students 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.
Pour about an inch of the blue water into the bottom of your glass or test tube.
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.
Add the yellow layer next using the same method and last the red layer. Stand back and admire your beautiful rainbow!
I hope your students love making the rainbow and learning about density in a fun way!
If you’re looking for another great science experiment that would be great for the science fair, you might like the simple circuit that we made. You can get all of the details for that project here.
See you next time!
I cannot find regular food coloring any where! Can gel food coloring be used??
I’ve never used gel food coloring, but if you can get it to mix with the water it would work just fine. Basically, you are just coloring the water in order to be able to see the layers.
Rebecca @ STEM Guide says
What a pretty density experiment!!
I didnt get layers..All the colours got mixed..what could have gone wrong?
Hi there. If you didn’t get layers, the sugar measurements may have been off. Also, the layers/colors need to be added VERY slowly otherwise it will all just become mixed. I hope that helps!
Would brown sugar work just as well?
My guess would be no since brown sugar contains molasses and would be a different density. But it is a science experiment, so it wouldn’t hurt to try it and see what would happen.
So fun! It looks awesome! Takes some time to do though but worth it! Kids thought it was cool but I think I had more fun then they did 😁
Ana P says
This was extremely fun. First we did not think it was working but then we put a light from behind and seen the wonderful masterpiece. We tried using a straw and it was a bit hard then we found some droppers and it was a whole lot easier. Thank you.
I was wondering about the straw and exactly how that would work. With the droppers, did you have to add the drops really slowly and one at a time? Or could you just squeeze it? Asking, because I want to try this with my two and threes. Some will be able to listen and add slowly l, but some may want to squeeze as hard as they can
Hi there. If you’re using a straw, you would plug the top end with your thumb and slowly let the liquid run out of it down the side of the inside of the jar. Same for the dropper. You don’t want to just “drop” the liquid in as it will then mix and you won’t get the density layers. You will just end up with a purple, brown mix. It may work for some of your twos and threes, but it may just be too much for some of them. Maybe an alternative is they watch you do it and then they could play with their own droppers in other colored water and make art on paper.