What you'll need:

Water
A clear plastic bottle
Vegetable oil
Food coloring
Alka-Seltzer (or other tablets that fizz)



Instructions:

Pour water into the plastic bottle until it is around one quarter full (you might want to use a funnel when filling the bottle so you don't spill anything).
Pour in vegetable oil until the bottle is nearly full.
Wait until the oil and water have separated.
Add around a dozen drops of food coloring to the bottle (choose any color you like).
Watch as the food coloring falls through the oil and mixes with the water.
Cut an Alka-Seltzer tablet into smaller pieces (around 5 or 6) and drop one of them into the bottle, things should start getting a little crazy, just like a real lava lamp!
When the bubbling stops, add another piece of Alka-Seltzer and enjoy the show!

Pink Tip: 

Adding more Alka-Seltzer to the bottle keeps the reaction going so you can enjoy your funky lava lamp for longer. If you want to show someone later you can simply screw on a bottle cap and add more Alka-Seltzer when you need to.

Make an Easy Lava Lamp