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  • Writer's pictureDarryl Silva

DIY Rainbow Jar – A Dense Tale of Density

DIY Rainbow Jar – A Dense Tale of Density

Here’s a free DIY STEM activity that is easy to do and pretty quick.  At 18 / 25 points, if you’re looking for a fun activity that uses mostly household ingredients and shows kids that liquids have different densities causing them to layer on top of one another, try the Rainbow Jar.

I did this activity with my 5-year-old and 2-year-old. They were able to help and they both loved it. Shout out to Playdough to Plato for the idea. Okay, we didn’t get the blue water to separate from the dish soap perfectly, but the wide eyes of two young girls were well worth the effort.

What:  DIY Rainbow Jar

Rating (out of 25): At 18 Points, the rating is Do IT if you’re short of time because it only takes 15 minutes!  (Fun = 3 + Confidence & Curiosity = 4 + STEM Aligned = 4, + Time Value = 2, + Cost = 5

Cost:  Free (if you have the materials)

Age: 4+ (adult supervision required and needed to ensure dish soap and rubbing alcohol doesn’t get in eyes or consumed).

Supplies / Ingredients:

  1. Mason Jar

  2. Honey

  3. Corn Syrup (coloured purple with food colouring)

  4. Dish Soap (green Palmolive works well)

  5. Water (coloured blue with food colouring)

  6. Olive oil or Canola Oil

  7. Rubbing alcohol (coloured red with food colouring)


  1. Make predictions. What do you think will happen as you add the items? Are some heavier than others?

  2. Pour ingredients into the Mason Jar one at a time in the following order: 1. Honey, 2. Corn Syrup, 3. Dish Soap, 4. Water, Oil, Rubbing Alcohol.

  3. Remember to pour each ingredient very carefully in the centre one by one with one except, the rubbing alcohol.

  4. It’s best to use a medicine dropper for the rubbing alcohol to layer it very carefully.

STEM Lesson: Density is mass per unit volume. A nice example to use is to ask your child to get two cups of equal size and to fill one with something lighter (like feathers) and one with something heavier (like magnets). For the exact same quantity, the magnets are heavier because they have a higher density. The same concept applies to liquids, so when you layer them carefully, the densest liquid (more molecules) goes to the bottom. And, when they are coloured – you get the Rainbow Jar.

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