Have you ever thought about building a lava lamp? Let’s find out how to do it together: just a few materials are enough to learn something about the density of liquids.
Create a lava lamp
Making a lava lamp requires materials that are easy to find. This is a great experiment with the density of liquids: it’s easy to do and very beautiful!
What to find?
- Some water
- A little vegetable oil (poor quality is suitable)
- Empty and transparent bottle
- A few drops of food coloring (blue or red)
- Effervescent tablet
How to make it?
To build a lava lamp, first pour a quarter of water into a bottle and color it with a few drops of dye. We used blue dye because it stands out so much compared to the color of the oil.
After that, on top of the first layer of our lava lamp, we create the second of oil. To do this, let’s pour two quarters into the bottle. Be careful not to completely fill the bottle with water and oil: we also leave some free space! The first thing we can observe is that oil and water do not mix: they remain two well separated layers.
At the moment we are ready to put our lamp into operation! Take a quarter of the effervescent tablet and drop it into the bottle, then close the cap. As soon as the tablet reaches the water layer, it will begin to boil. Bubbles of colored water will gradually appear and rise up until the effect reaches its maximum in a real lava lamp.
We pay attention to the size of the effervescent tablet. It doesn’t need to be that big: a quarter or half is more than enough. But let’s not put too small a piece of it because it may not sink through the oil and never reach the water. In this case, the lamp would not work!
The effect will disappear shortly after, but we can replicate it by adding other pieces of effervescent tablet.
Finally, we can make a real glowing lamp out of it by adding light to the base of the bottle, like a mobile phone flashlight.
When the life of our lava lamp is over, it is important that its contents are not dispersed into the environment. In fact, its chemical components could damage the ecosystem if they ended up on the ground or in a drain, as happens with soap. Then we empty the contents of the bottle into the toilet or sink.
Explanation of the phenomenon
In this experiment, we encountered two different phenomena. Let’s find out what causes them!
Build Lava Lamp Water and oil do not mix. This is because oil is lighter than water. Just as a piece of wood floats in water because it is lighter, so does oil. In fact, if we could see through a supermicroscope, we would realize that the particles (molecules) that make up oil are wider and rarer than those that make up water, making oil lighter and able to float above water.
The bubbles of water rise and fall
When we drop an effervescent tablet into a bottle, it first goes through the entire oil layer. When it meets water, it begins to boil, which produces air. Being lighter than water, small air bubbles rise up. But they are also lighter than oil, so they continue to grow when they encounter it.
On their way up, however, they also carry some water: these are the colored bubbles that we see rising through the oil, when the air bubbles reach the top of the oil layer, and come into contact with the oil. air, the colored water bubbles are left alone on top of the oil. But, since water is heavier than oil, the bubbles descend downwards until they meet the layer of water again.