Lava in a Cup Experiment

It turns out that the Crystal Egg Geode activity I mentioned yesterday requires quite a few items that I currently do not have in my house.  My daughters and I did blow out a couple of eggs which I'll show in a future post.  Our main experiment yesterday was the Lava in a Cup experiment.  To complete this experiment you need vegetable oil, salt, water, food coloring, and a clear cup.

First fill the cup 3/4 full of water.  Next put in 1/4 to 1/2 cup of vegetable oil.  Here you can point out to your child that the oil floats to the top of the water.  Oil has a lower density than water so it rises to the top.  This is clearly seen through a clear cup.  Add a few drops of food coloring (your choice of color).  The food coloring serves no real purpose aside from changing the color of the water.  Now take a spoonful of salt and sprinkle it on top of the oil.  You should see something similar to what I recorded in the video below.

The salt sprinkled on top sinks through the oil and falls to the bottom of the cup.  Along the way however, it takes some oil with it.  Once the salt dissolves out of the oil, the oil bubbles rise back to the top!  My kids loved watching the bubbles rise to the top.  We dropped several spoonfuls of salt into the jar.  At one point we decided to test what would happen if we stirred the mixture with a spoon.  Would everything mix together?  The answer is yes, but the water becomes very cloudy due to all the salt, so it was hard to see.

This is a great Saturday activity for young kids.  It requires few supplies, is easy to set up, and produces quite the show.