A clean plastic bottle (try to find one with smooth sides)
Fizzing tablets (such as Alka Seltzer)
1. Fill the bottle
Pour water into the bottle until it is about a quarter full.
2. Add vegetable oil
Pour the vegetable oil into the bottle until it is almost full — you can use a measuring cup with a spout or a funnel to avoid messes. It may take a couple of minutes for the oil and water to separate.
3. Add a few drops of food coloring
Watch as the color sinks through the oil. Did your drops of color mix with the water immediately or float in between for a few minutes?
4. Drop half of a fizzy tablet into the bottle
Get ready … here come the bubbly blobs!
For a fun extra step, grab a flashlight and turn off the lights! Drop in another half tablet, and this time, shine the flashlight through the lava lamp while the blobs are bubbling!
The oil floats on top of the water because it is less dense – or lighter – than water. The food coloring has the same density as the water, so it sinks through the oil and mixes with the water. When you add the tablet, it sinks to the bottom, starts to dissolve, and creates a gas: carbon dioxide. Carbon dioxide, an element present in the air we breathe, is lighter than water, so it floats to the top. The air bubbles bring some colored water with them to the top. When the air comes out of the colored water blob, the water gets heavy again and sinks. It does this over and over again until the tablet is completely dissolved.
Here are a few follow-up questions you can explore!
What happens if you put the cap on the bottle after adding a fizzy tablet?
What happens if you drop a whole tablet into the bottle?
When the tablet stops bubbling, try sprinkling some salt into your lava lamp. What happens?
Follow along for new experiments each month and contact SciGenius to learn more about our STEAM programs! From in-school enrichment and after-school programs to science summer camp, we are dedicated to making art and science easy to access for kids in Ashburn, Virginia and the surrounding areas. Contact us for more information and register your kids today!
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