Try this at home
Make Your Own Lava Lamp
Experiment with chemistry and make concoctions for your Mad Scientist’s Laboratory!
What you’ll need:
- Clean, disposable, water or soda bottle with lid
- Vegetable oil
- Antacid tablets
- Food coloring
- Optional: glitter, beads, funnel, flashlight
Here’s what to do:
- Fill your bottle about ⅔ of the way full with water.
- (Optional bling!) Sprinkle in some glitter and beads, only about 1 tsp of each.
- Add vegetable oil to the bottle until the bottle is nearly full. Leave about ¼ inch of space near the top.
- Add 2-3 drops of food coloring (for a 16 oz. bottle). Watch what happens!
- Screw the lid on tightly.
- Carefully, making sure there are no leaks, flip your bottle upside down. Watch what happens!
Take it further:
- Open your bottle and slowly add 1 tsp of salt. What happens? Where does the salt go? Add more salt. How long can you make your lava lamp bubble using 1 tsp of salt?
- Break an antacid tablet into 3 or 4 pieces. Add 1 piece to your bottle. What happens? Where does the tablet go and what happens to it? How is this different from what happened with the salt? Add the rest of the antacid pieces, and watch your lamp bubble!
- What happens if you use warm water? Ice water? Does this affect how the salt or antacid work?
- Shine a flashlight through the bottom of the bottle while your lava lamp is moving. What does it look like? Do you notice anything different? Does the light reflect off of any of the pieces inside your lava lamp?
What’s going on?
There are two concepts working to make your lava lamp work. One is density – how tightly packed the molecules of something are (or how much of it fits in a certain space). Water molecules pack more tightly than the larger oil molecules, so water is more dense than oil. For example, 1 cup of water is heavier than 1 cup of oil because of density! This is why the oil sits on top of the water, and one of the reasons why oil and water don’t mix. The other reason is polarity. In chemistry, “like dissolves like” which means that molecules like to mix with molecules that are similar to them. In your lava lamp, the oil and water don’t mix because they are not similar; water is polar and oil is nonpolar. Polar molecules have positive and negative ends (you can think of it like a magnet), so they are attracted to each other (positive ends attracted to negative ends). Water molecules like to mix with and be around other water molecules (or other polar molecules). Oil, on the other hand, is nonpolar; it doesn’t have positive and negative ends – it’s neutral. Since oil doesn’t have the polar ends like water, it’s not attracted to the water nor the water to it. Polar likes polar and nonpolar likes nonpolar! Where did the food coloring mix in? Do you think the food coloring is polar or nonpolar?
When you add the antacid tablet, it fell to the bottom and began dissolving in the water, creating a gas. The gas bubbles take some of the colored water (and glitter and beads) up with them when they try to escape the bottle, but once the gas bubble escapes the bottle, the water (and glitter and beads) that came with it are in the oil where they don’t mix and are too heavy, so they fall back down!