What is a Pure Substance in Chemistry?

In chemistry, a pure substance is a material that consists of a single substance and contains no other substances or impurities. A pure substance has a fixed composition, meaning that it always contains the same proportion of atoms or molecules.

Pure substances can be either elements or compounds. Elements are pure substances made up of only one type of atom, while compounds are pure substances made up of two or more different elements chemically bonded together.

Examples of pure substances include:

* Elements such as gold (Au), silver (Ag), and copper (Cu)
* Compounds such as water (H2O), table salt (NaCl), and sugar (C6H12O6)

In contrast, a mixture is a combination of two or more substances that are not chemically bonded together. A mixture can be either homogeneous (consisting of the same composition throughout) or heterogeneous (having different compositions in different parts). Examples of mixtures include:

* Salad dressing (a mixture of oil, vinegar, and spices)
* Air (a mixture of nitrogen, oxygen, and other gases)
* Soil (a mixture of organic matter, minerals, and water)

In summary, a pure substance is a material that consists of only one substance and has a fixed composition, while a mixture is a combination of two or more substances that are not chemically bonded together.