Matter and Its Properties
Matter can be either a pure substance or a mixture of substances. Pure substances (elements or compounds) have constant composition and properties throughout any sample. When substances are mixed, we get mixtures that can be either homogeneous (uniform throughout) or heterogeneous (not uniform).
Properties of matter help us identify and separate mixtures. Physical properties like density, particle size, and boiling point allow for separation methods including evaporation, filtration, distillation, and chromatography.
Elements exist in different physical states at room temperature. Bromine and mercury are the only liquid elements, while noble gases and several others (nitrogen, oxygen, fluorine, hydrogen, chlorine) exist as gases. Most elements are solids. Some elements naturally exist as diatomic molecules (BrINClHOF).
Science Hack: Remember the elements that exist as diatomic molecules with the mnemonic "BrINClHOF" (bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, fluorine)!
