The lava lamps you see in the stores use wax and heat to work. The light bulb heats up the wax at the bottom of the lamp. As it gets hot, the wax expands and it’s density decreases. When the density of the wax is lower than the density of the water, the wax floats to the top of the lamp. When the wax is at the top and away from the light bulb, it begins to cool back down. As it cools, it shrinks and it’s density increases. This makes it sink back to the bottom where the process starts all over again!
We are going to make a lava lamp that doesn’t need electricity and heat.
You’ll need:
A flat bottomed test test with a cap or a small jar
Food coloring
Fizzy Tablets (Alka-seltzer type tablets work well)
Some cooking oil (mineral oil or baby oil also work well)
Water
- Food coloring can stain so be sure you are wearing clothes that are ok to get dirty. Be sure to protect your work surface too.
- Put a few drops of food coloring in your tube.
- Fill the tube about half way with oil. What did the food coloring do?
- Now fill the rest of the tube with water. What did the food coloring do this time?
- Put the cap on your tube and gently shake the tube to mix everything together. Let it sit for a few minutes and watch what happens.
- Once everything settles back down, you’ll have two layers – a colored water layer and a layer of oil.
- Now comes the fun part! Break a fizzy tablet into smaller pieces. Drop a piece into the tube and watch what happens! What does the tablet do when it hits the oil? What does it do once it sinks down to the water layer?
If you run out of tablet pieces, you can still make and watch bubbles by gently shaking the capped tube first. Now, instead of rising, the colored bubbles sink! Why?