The properties of helium and hydrogen gases are discussed in this video adapted from the National Science Center. Certain chemical elements undergo no visible reaction when introduced to other chemical elements. Gases that fall into this category are called inert gases. In contrast, gases that are changed in some way are called reactive gases. To demonstrate that helium is inert and hydrogen extremely reactive, the presenter puts a flame up to balloons containing each gas. (Note: This demonstration was performed by a trained professional. Do not try this at home.)

This video is available in both English and Spanish audio, along with corresponding closed captions.