I love science experiments about density and making your own “lava lamp” is no different! No, it doesn’t light up like a real lava lamp, but you can create the same “bubbled” effect in just 4 easy steps and really let kids see a hands-on visual method for understanding density even further. I have done this experiment both at home with my children and in a 2nd grade classroom. It is a little pricey to do in a larger classroom setting so if you need a cost effective experiment with similar results check out our Lava Science Experiment in a Bowl.
empty plastic bottle
Step 1. – Pour the oil into your empty plastic bottle, about 2/3 full.
Step 2 – Pour a few inches of water in, but leaving empty room at the top.
Step 3 – Add food coloring! I usually give it one good squeeze.
(Note – you can mix colors but as you see ours below it can get quite murky!)
Step 4 – Add 2 Alka Seltzers in per bottle. (1 Alka Seltzer is OK if you’re on a budget)
***NOTE*** Do NOT put the lid on while the Alka Seltzer is in the bottle. You will explode your bottle!
Pretty cool huh? My kids, being boys of course, love mixing colors to make weird funky purplish brown shades as you can see above! When your Alka Seltzer is finished “bubbling” you can screw the lid back in place and keep it for later! Just re-add 1 or 2 Alka Seltzer tablets when you want your bottle to look like a lava lamp again!
1. Why don’t the oil & water mix?
Because the oil is less dense than water so it floats to the top. The molecules in water are more tightly packed together than in the oil causing it to have a higher density.
2. Why doesn’t the food coloring mix with the oil?
Food coloring is water based thus it won’t mix with oil because it is more dense. The food coloring sinks to the bottom and mixes with the layer of water.
3. Why does the Alka-Seltzer cause the water to rise?
The Alka-Seltzer produces carbon dioxide, a gas, which bubbles in the layer of water. As the bubbles rise it carries the water up in into the layer of oil. The oil and water don’t mix so the water beads together into a “bubble” as it travels through the oil.
BUY Your OWN Lava Lamp and let your kids compare the difference to their homemade one!