Whack-a-packs are little self inflating balloons that rely upon an acid base reaction for them to explode and inflate. Hitting the package bursts a tiny liquid pack inside the balloon and initiates the reaction between citric acid and sodium bicarbonate. The reaction is endothermic, so if you have the chance to try these out, grab the balloon as soon as it explodes out of the packaging…it will feel cold! #chemistry #themoreyouknow #chemteacherphil #neutralization #chemistryexplained