Truth be told, this "lava" doesn't light up. But it's still guaranteed to generate some oohs and ahs from your kiddos. Here's how we made our DIY lava lamp.
Oil (we used baby oil, but cooking [e.g. vegetable] oil will work too)
3/4 cup water
alka seltzer tablets
empty plastic water bottle
How to Make It
Pour the water into your bottle. (Use a funnel if you've got one.) Now pour the oil in, filling the bottle 2/3rds full.
Invite your child to observe the contents of the bottle. Did the oil and water mix? The oil will be sitting on top of the water because it's the less dense of the two liquids.
Add several droplets of food coloring into the bottle. Again - observe and hypothesize. Why doesn't the oil turn color? Hint: it's water-based!
Now you're ready for the fun part. Break up a few alka seltzer tablets and drop them in the bottle. Watch the reaction (both inside AND on your child's face) as blobs of colored water rise up through the oil just like in a lava lamp!
When the fizzing stops and the oil and water separate again, you can add more tablets to keep the excitement going.
My son didn't know quite what to expect but found the chemical reaction fascinating, so much so that he had to invite a neighborhood friend over to see it, and then capped the bottle to take to his house so his mom and little brother could witness it too! And when his dad and little brother got home, yep, more tablets were added so they could also see it.
Any activity that makes my son this enthusiastic gets an A+ from me!