Observed in Illinois on the first Monday of March every year, the holiday ostensibly honors Polish-born Revolutionary War cavalry officer Casimir Pulaski, though for most school kids with a four-day week, itâs probably just another sweet, sweet sleep-in day.
Yes, in chemistry a pure substance means either an element or a compound. Thus, hydrogen, oxygen, sodium, iron, copper etc. are pure substances; and so are compounds such as water, sugar, ammonia, sodium chloride, methane, ethanol etc. A compound is composed of two or more elements combined in a fixed ratio by mass. Like an element, a compound also has a distinct chemical identity. A mixture is not a pure substance as it is a collection of two or more elements/compounds in varying ratio. Air, sea water, gasoline, vegetable oils, steel etc. are mixtures.
1 Ammonia is a toxic gas or liquid that, when concentrated, is corrosive to tissues upon contact. 2  Exposure to ammonia in sufficient quantities can be fatal. 3  One of the highest production-volume chemicals in the U.S., concentrated ammonia is used in manufacturing, refrigeration, and agriculture (as a fertilizer). Clear, colorless liquid under pressure. 2  DESCRIPTION: For the purposes of this card, ammonia refers to solutions that are 50% ammonia or greater, ammonia anhydrous, and ammonia anhydrous liquified, unless otherwise specified. 3  Ammonia is a toxic gas or liquid that, when concentrated, is corrosive to tissues upon contact.