9781422279472

Hydrogen H 1

WORDS TO UNDERSTAND airship an aircraft that uses lighter-than-air gas (either hydrogen or helium) to float density a measure of how tightly packed together a substance is nuclear weapon any weapon that uses a nuclear reaction to set off an explosion phlogiston a substance proposed by 18th-century chemists that was supposedly released when other substances burned solubility the ability of a substance to dissolve in a liquid