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.
Therefore, we can broadly categorize matter into two categories as pure substances and mixtures. Mixtures can be mainly divided into two, as homogeneous mixtures and heterogeneous mixtures. Pure Substance. Pure substance cannot be separated into two or more substances by any mechanical or physical method. Therefore, pure substance is homogenous. It has a uniform composition throughout the sample. Further, the properties of it are also uniform throughout the sample. Elements are pure substances. An element is a chemical substance, which consists of only a single type of atoms; hence, they are pure. There are about 118 elements given in the periodic table according to their atomic number. For example, the smallest element is the hydrogen.