2. Two Types of Substances. Some substances are made of only one kind of atom. Other
substances are made of more than one kind of atom. How are the properties of these two
types of substances different?

Elements and compounds

Explanation:

Substances are purely classified as pure and impure substances.

Pure substances are those with a definite composition which are simply elements and compounds.

Impure substances are those with an indefinite composition which are mixtures.

Elements are pure substances that are made up of only one kind of atom. About 117 known elements occur naturally. Compounds are distinct substances made up of two or more kinds of atoms/elements joined together in a definite grouping.

How are their properties different;

Elements are made up of just a single type of atom where as compounds are made up of different atoms. Elements have a limited number whereas compounds are highly varied in nature. The properties of an element is a function of the type of atom that makes it up but the properties of a compound is distinct from those of the individual elements. Symbols are used to represent elements whereas chemical formulas are used to denote compounds.