Separation of substances is the process of isolating or removing one or more substances from a mixture. It is an important concept in chemistry and is used in various fields such as medicine, industry, and research. There are several reasons why substances need to be separated, which are explained in detail below:

1. Purity: Separation of substances is often done to obtain pure substances. A pure substance consists of only one type of particle, either an element or a compound. By separating impurities or other substances from a mixture, we can obtain a pure substance that can be used for various purposes.

2. Analysis: Separation of substances is crucial for analytical purposes. Scientists and researchers often need to analyze the composition of a mixture to understand its properties or to identify the presence of specific substances. By separating the components of a mixture, they can isolate and study each substance individually.

3. Recycling: Separation of substances is important for recycling processes. Many materials, such as plastics, metals, and paper, can be recycled to conserve natural resources and reduce waste. Separating these materials from a mixture allows them to be reused or processed into new products.

4. Extraction: Separation of substances is used in extraction processes to obtain valuable or desired components. For example, in the extraction of metals from ores, various techniques such as filtration, magnetic separation, and distillation are employed to separate the metal from impurities.

5. Purification: Separation of substances is also used for purification purposes. For example, in the purification of water, various methods such as filtration, sedimentation, and chlorination are employed to remove impurities and make it safe for consumption.

6. Formulation: Separation of substances is often necessary in the formulation of products. For example, in the production of medicines, separation techniques are used to obtain pure active ingredients, remove impurities, and ensure the desired concentration and quality of the final product.

In conclusion, separation of substances is important for various reasons including obtaining purity, analyzing mixtures, recycling materials, extracting valuable components, purifying substances, and formulating products. It is a fundamental concept in chemistry and is widely used in different fields for a variety of purposes.