Science Experiment: Lava Lamp

I love an easy science experiment that includes supplies I already have and get a great reaction from my students.  Here is one of them.

Materials Needed:

A jar or clear cup

Oil

Water

food coloring

alka seltzer tablet

Instructions:

1.  Fill a container 1/2 to 3/4 full with oil.  I used vegetable oil but you can also use baby oil if you want the oil to be clear.

2.  Fill the rest of the container with water.

3.  Add 3-5 drops of food coloring to the jar.  Observe how the food coloring stops at the bottom of the oil but doesn't mix with it and then drops to the water where it mixes with the water and changes the color.

4.  Break up the alka seltzer into 1/4 or 1/2 pieces and drop into the jar.  Observe.  When the bubbling stops add another alka seltzer tablet.  Repeat as much as you want.

The science behind it:

Oil and water don't mix.  The oil will stay on top of the water.  The Alka-Seltzer tablet reacts with the water to make carbon dioxide gas.  These bubbles attach to the colored water and cause them to float to the top.  When the bubbles pop they float back to the bottom.