Science Experiment: Make a Diet Coke+Mentos Rocket

Step 6: Do the following quickly! Unscrew the cap about halfway, then pick up the bottle with the cap pointing outward, take a couple of running steps and then spike the bottle hard, cap-first, on the pavement -- like you're a football player celebrating a touchdown. Then jump back. If you do it right, the cap will come off the Diet Coke bottle and a brown jet of suds will propel the homemade rocket in an upward arc. Make sure you aim the rocket so that it flies up and comes down over an open space — and doesn't smash into someone's parked car or land in your neighbor's flower bed (like ours did!).