Materials
- Clear plastic or glass bottle (16-20 oz)
- Vegetable oil
- Water
- Food coloring (any color)
- Alka-Seltzer tablets
- Funnel for pouring
Procedure
- Fill the bottle about ¾ full with vegetable oil.
- Fill the rest of the bottle with water, leaving some space at the top. Wait for the water and oil to separate into two layers.
- Add 10-15 drops of food coloring to the bottle. The coloring will pass through the oil and mix with the water below.
- Break an Alka-Seltzer tablet into smaller pieces.
- Drop one piece of the tablet into the bottle and watch the lava lamp effect!
- When the bubbling stops, add more pieces to keep the effect going.
Choose Your Learning Level
Elementary
This experiment shows how oil and water don't mix and how bubbles can move around to make a cool lava lamp look. When you drop the tablet in, it makes bubbles that float up and down!
Discussion Questions
- Why do you think oil and water don't mix?
- What do the bubbles do inside the bottle?
- Can you describe the colors and movements you see?
Middle School
Oil and water separate because they have different densities and don't mix (are immiscible). The Alka-Seltzer reacts with water to produce carbon dioxide gas bubbles that rise through the oil, creating the lava lamp effect.
Discussion Questions
- What causes the bubbles to move up and down?
- How does density affect the layers in the bottle?
- What gas is produced by the reaction?
High School
The experiment demonstrates principles of density, immiscibility, and chemical reaction kinetics. Vegetable oil is less dense than water, so it floats on top. The Alka-Seltzer tablet reacts with water to produce CO₂ gas, which forms bubbles that rise through the oil, creating the lava lamp motion due to buoyancy and gas release.
Discussion Questions
- Explain the roles of intermolecular forces in the separation of oil and water.
- Describe the chemical reaction taking place between Alka-Seltzer and water.
- How would changing the temperature affect the reaction rate and lava lamp effect?