We enjoyed making a homemade lava lamp with alka seltzer, now try a fun lava lamp experiment with salt. Explore what happens when you add salt to oil and water. There are tons of ways to have fun with science all year round!
Lava Lamp Experiment With Salt
Field of Science: Physical Science
Recommended Grade Level: K-5
Science Concepts Explored: Density, buoyancy, solutions, chemical vs. physical change
Can you use salt instead of Alka Seltzer in a lava lamp? You betcha!
Supplies:
- Bottle or jar
- Water
- Vegetable oil
- Salt
- Food coloring (optional)
Instructions:
STEP 1: Pour water into the jar.
If using food coloring, add a few drops to the water now.
STEP 2: Pour in 1/4 cup of vegetable oil. What do you notice?
STEP 3: Sprinkle a spoonful of salt into the jar.
Get this free printable salt lava lamp project!
The Science Behind The Experiment
This lava lamp experiment with salt is a great way to visually demonstrate that oil and water don’t mix and how differences in density affect their interaction.
First, you pour water into a container and then add oil. The oil floats on top of the water because it is less dense, and they remain separate since oil and water don’t mix due to their properties (oil is nonpolar, and water is polar).
💡 Here is a more detailed explanation of why oil and water don’t mix.
When you add salt to this mixture, it sinks to the bottom because it is denser than both water and oil. As the salt sinks, it drags some of the oil down with it in the form of clumps.
Once the salt dissolves in the water, the oil that was temporarily dragged down rises back up to the top because it’s still less dense than water. This creates a “lava lamp” effect, where blobs of oil move up and down in the water.
💡 Explore more density experiments [here].
Make It a Science Project
Turn this simple experiment into a full science project! Try these ideas:
Learn about using the scientific method, writing a hypothesis, and choosing variables
- Question: Does the type of salt matter (table salt vs. rock salt)?
- Hypothesis: Predict which salt will create a bigger or longer eruption.
- Experiment: Test different types and amounts of salt and record your observations.
- Data Collection: Create a simple chart to record the length of eruptions or the height of the oil bubbles.
- Conclusion: What did you learn about density and how materials interact?
Explore More Oil and Water Experiments
Try this simple oil and water experiment with food coloring!
How about a classic homemade lava lamp with oil, water, and alka seltzer tablets!
Want to see how you can mix oil and water using an emulsifier? Check out our salad dressing activity.
Making a density tower is another great way to observe how not all liquids weigh the same.
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