* Elements: Elements are the basic building blocks of matter and cannot be broken down into simpler substances by chemical means. There are 118 known elements, each with a unique atomic number.
* Compounds: Compounds are substances that contain two or more elements chemically combined in a fixed proportion. Examples of compounds include water (H2O), carbon dioxide (CO2), and sodium chloride (NaCl).
* Mixtures: Mixtures are combinations of two or more substances that are not chemically combined. The composition of a mixture can vary, and the substances can be separated by physical means, such as filtration or distillation. Examples of mixtures include air, salt water, and gasoline.
In contrast to pure matter, impure matter is matter that contains a mixture of different substances. For example, air is a mixture of nitrogen, oxygen, and other gases.
