This modified version of a lava lamp is definitely one of our favorite cool science experiments! It’s a super fun way for kids to explore the density of liquids using materials you have right in your kitchen.
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We have a lot of cool science experiments for kids on Buggy and Buddy like this Baggie Burst experiment and exploring Colorful Chemical Reactions! I think this exploration of liquid density ranks right up there with our favorites!
With just a few household materials, children can explore the density of liquids and even practice mixing colors in a super fun way! (This post contains affiliate links.)
See it in action here!
Cool Science Experiments: Density of Liquids
Materials for Science Experiment
- Clear glass
- Water
- Vegetable oil
- Food coloring
- Salt
Science Experiment Procedure
1. Fill your clear glass about 2/3 of the way with water.
2. Pour vegetable oil into your cup. (You want to create a layer that’s about 3/4-1 inch high.) What happens to the oil after you pour it in your cup? Why do you think this happens?
3. Add one drop of food coloring to the cup. What happens to the drop of food coloring? Why do you think this happens?
4. Sprinkle salt into your cup and watch what happens!
5. Continue adding more salt and observe. (The kids started by doing small sprinkles of salt, then progressed to adding big pinches of salt, and then spoonfuls of salt.)
6. Allow time for your child to explore the setup on their own. Lucy (6 years old) wanted to add different colors of food coloring to her cup to see what would happen.
This science activity was a great sensory experiment for Theo, my 3 year old. He loved watching all the movement in the cup and would even stick his finger in the liquids to see what would happen!
What’s Going On?
In the beginning of the experiment, the oil settles above the water because it is less dense. When you add salt to the to the cup, the salt sinks to the bottom of the cup since it is heavier than the other two liquids. The salt carries a blob of oil with it. As the salt begins to dissolve in the water, it releases the oil which floats back up to the top.
Be sure to try this similar density experiment– comes with a free printable too!
Want to go even further?
Even more activities to inspire creativity and critical thinking for various ages.
1. Try this Dancing Raisins experiment. How is it similar to the one you just did? How is it different?
2. Explore the density of objects in this simple sink and float experiment.
3. Try this Seven Layer Density Column experiment.
What an amazing way to learn. Love. Stepping in from Tuesday tots.
This looks so cool! And so pretty! I can’t wait to give it a try.
Loved it!! Tried with our little guy tonight. We added pepper after the salt, which was pretty cool! The pepper floated in the oil and when we took a plastic stick to push the pepper down it stuck to the stick until we pulled the stick back up.
I LOVE how you added the pepper! Such a neat idea for kids to explore! So so glad you enjoyed it! 🙂
Fun fun fun !!!!!!!!!!!!!!!!!!!!!!!
I tried this and it works! The explanation, however, doesn’t seem thorough enough? Does the Salt make the food color’s density greater, therefore, bringing the color down into the color portion?
Glad you enjoyed it and thanks for the comment! The food coloring is water soluble. It will not mix with the oil, but will mix with the water. Since it was added after the oil in small amounts, it remands suspended in the oil and won’t mix with it. (If you squeeze a ton at once- which my son happily tried- it will go directly into the water.) The salt is heavier than both the oil and water, so when it lands onto the drops of food dye, it pulls the dye and blobs of oil down with it into the water where the dye will spread.
Thanks for the further explanation. We’re using this for a homeschool lesson and I like being able to answer all of her questions.
Not just for the little ones. I had some bored teenagers here on a Saturday night who really got into this
really cool my kids loved it
This is a very easy experiment to try, I really liked it.