Water Lava Lamp (learning Density)

Want to go back to your Grateful Dead days, but can't get yourself to order a lava lamp from Hot Topic? Or maybe you want to introduce kids to the amazing wonders of density as it relates to temperature, and you're looking for an accessible project?

Either way, you're in luck, because the water lava lamp not only produces more psychedelic images than you can shake a purple giraffe at, but it also is a wonderful and cheap way to predict, experiment, and record results in dealing with convection, water currents, and buoyancy.

You'll lava it!

• What: Water Lava Lamp
• Concepts: density, buoyancy, temperature, convection
• Cost: Free* (close, anyways)
• Time: Quick! (after you freeze the ice)
• Materials:
  • Big Clear Tupperware
  • Food coloring
  • Small Bottle
  • Water
• Tools:
  • Ice Cube tray
  • Water heating device
  • Syringe or Pipette (or careful pouring)

Let's convect!

For the ice, simply add a lot of food coloring to water in an ice cube tray. I meant to do blue, but am colorblind, so purple it is! Once your ice is frozen, you can remove the cubes and start the experiment right away. What you'll find is pretty beautiful, and usually involves long ribbons of color headed to the tub's floor.

Note: When I'm working with kids, I often preface this with asking where the warmest part of a pool would be (ignoring sun and location of heaters). I have them predict where the cold water from the ice will go, and get them ready to record results.

The red hot is also straightforward. Heat up some water to just below boiling, and pour into a safe receptacle. Take your small bottle or jar, and add a couple drops of red food coloring. The shape of the bottle will vary the results quite a bit, so play around with whatever receptacle you can find!

Use a syringe or pipette to take a bit of the hot water, and add it to your bottle. Shake it a bit to mix, and then place it upright in the bottom of your tub. It should begin to "volcano" shortly after, sending hot water to the surface.

Have fun as your lava lamp takes action.There are many things to observe beyond the "hot goes up, cold goes down" lesson in density. Currents from the red often push the ice cube, and make it melt in interesting ways. Additionally, the hot water often ends up trailing back down over time and turning in to donut-shaped patterns if the tub is left undisturbed.

If motion has stopped, simply take out your bottle and add more hot red water, or drop in a new ice cube.

Have a great time learning about density, and if applicable, hopefully this can help fill in some of those gaps in memories of the 60s. :)

As always, keep exploring!