There are three different technologies that fall into the catapult category: the ballista, the trebuchet and the catapult. Check out this HowStuffWorks podcast to learn more about the differences between catapult technologies.
The idea behind a water softener is simple: the calcium and magnesium ions in hard water are replaced with sodium ions. Learn more about the harmful effects of hard water -- and the benefits of soft water -- in this HowStuffWorks podcast.
Learn how the length of hydrocarbon atom chains have different properties, producing substances such as kerosene, methane and other forms of fossil fuel. Check out this HowStuffWorks podcast to learn more about fossil fuels.
The fizzing you see when you drop an Alka-Seltzer tablet in water is the same sort of fizzing that you see from baking powder. This reaction is caused by an acid reacting with a base. Check out this HowStuffWorks podcast to learn more.