Dihydrogen monoxide

Thus ice contracts when melting, ice being a regular and rather open structure of hydrogen and oxygen atoms, while water is a collection of dihydrogen-monoxide (H₂O), tetra-hydrogen dioxide (2H₂O), and more complex molecules.

Source: wiktionary

The Invisible Killer Dihydrogen monoxide is colorless, odorless, tasteless, and kills uncounted thousands of people every year. Most of these deaths are caused by accidental inhalation of DHMO, but the dangers of dihydrogen monoxide do not end there.

Source: wiktionary

There was no point in buying bottled water, he said, dihydrogen monoxide would be in there too, although you could get rid of it by boiling your water for long enough.

Source: wiktionary

One-by-one the warning fliers turned up in mailboxes around Wylie Heights in North Sewickley, Beaver County: It advised, there is a chemical in your water supply called dihydrogen monoxide. Tasteless and colorless, dihydrogen monoxide was blamed for a trio of ills: severe hydration, frequent urination and possible death. In fact, the flier said, dihydrogen monoxide kills thousands every year. […] Dihydrogen monoxide is the chemical name for water, and a quartet of Riverside High School students are up to their necks in the hot kind after their Internet-inspired prank made dozens of homeowners not readily acquainted with chemical terms hyper over hydro.

Source: wiktionary