The lava lamps had about a 1/3 of the bottle of water, then the rest was oil. You can use either baby oil or vegetable oil (I am sure you could use just about any cooking oil really). Then you add a few drops of food coloring to the bottle. Next, you break up Alka Seltzer tablets and put the pieces into the bottle and watch what happens. We found that the baby oil didn't work quite as well as the vegetable oil in our experiment. We also took this experiment into the dark bathroom and lit up our lava lamp with a flashlight..very cool!!!
For the mini volcanoes, I gave the boys a cup about 1/2 full of vinegar and food coloring and a small container of baking soda and a spoon. They got to see what happened when they put tiny amounts of baking soda into the solution and what happened when they put lots of baking soda into the solution. They had fun with both experiments! :)