N.C. Science Festival: Try this easy lava lamp experiment

All you need is a cup, water, oil, food coloring and water to make your own lava lamp at home.

Posted 12:45 a.m. Apr 1, 2014 — Updated 12:45 a.m. Apr 1, 2014

The N.C. Science Festival kicked off last week and runs through April 13, offering all sorts of science-themed activities for kids to adults.

"There are science expos (think: “science street fairs”) happening across the state, in addition to events at libraries, museums, parks, sporting events, and even a cemetery," festival director Jonathan Frederick told me in this Q&A.

As part of the festival, school students across the state have taken part in science-themed programs. Leaders developed a free curriculum guide that takes participants step-by-step through a variety of activities and explains the science behind each of them.

The guide is free. Parents and educators are invited to email the festival to receive their own free lesson plans for hands-on science activities. Just email ncscifestschools@unc.edu for the link. I highly recommend it. It has some great activities you can do now and all year.

One of the activities is making your own lava lamp. This activity requires a clear plastic cup, water, oil, food coloring and salt. I tried this with my girls who were pretty amazed at what happens when you add the salt to the cup. Watch the video to see what happens.

Here's what you do, following the directions from the festival's guide, which has a lot great information in it:

1. Fill your cup ½ full with water.

2. Add oil until it forms a layer about ½-1 inch thick at the top of the water.

3. Drop 3 drops of food coloring into the cup. What happens?

4. Sprinkle a little salt into the cup and observe. What do you think is going on?

5. Repeat! You may add more food coloring if needed. Do not put too much in right away; this will make the water too dark to see the cool effect.

And here's the science behind it, according to the festival: For our lava lamps the materials we use have different densities. In the instance of water and oil, water is more dense than the oil which is why the oil floats on top of the water. When we add the salt, which is heavier than water, it sinks to the bottom. But, as the salt sinks to the bottom it brings some oil from the top along with it. As the salt begins to dissolve in the water, the oil is “released” and floats back up to the top of the water.

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