Why does your bicycle tire sometimes go flat? Why are there gaps in railroad tracks? Do you know how a thermometer works? Find out by doing the fun, easy-to-follow experiments in this book. Unlock the secrets of solids, liquids, and gases! Learn all about density, pressure, collisions, expansion, contraction, and more! All you need are some common household materials. If you are interested in competing in a science fair, you can get many great ideas that will help you create a unique, award-winning science project. Book jacket.