This science project will be a great craft for your kids at their free time. You can make it with your children or they can make it by themselves. You will need a plastic water bottle, empty (tall and skinny bottle), food coloring and alka seltzer tablets. Fill 3/4 of the bottle with vegetable oil. Then fill the rest of the bottle with water, leaving about an inch from the top. Now add food coloring, adding about 10 drops. Now break up alka seltzer tablet into several pieces (about 4) and have your child drop them into the solution one at a time and observe the effect! Now repeat with the other bottles, using different food coloring. Enjoy!