A pure material that consists of only one type of atom and cannot be broken into two or more basic substances by physical or chemical means is referred to as an element. For example zinc, sulphur. An element is homogeneous; it is a pure product, made up of just one kind of atom.

Compounds are made up of one or more elements and are described by chemical formulas. A compound comprises atoms of various elements which are chemically mixed in a fixed ratio. A compound can be broken down into simpler compounds using chemical methods/reactions. A compound is expressed by a formula—for example, water (H2O), sodium chloride (NaCl), magnesium oxide (MgO).

In chemistry, when two or more substances are mixed without taking part in a chemical change, the resulting substance is called a mixture. The result formed by a combination of substances does not lose its individuality or is chemically combined. Mixtures are a single product of a mechanical blending or mixing of chemical substances such as elements and compounds.

Most of the time, the substances we see around us are not in their pure form. Therefore, there are several types of separation techniques used to segregate a mixture of substances. 

• Sieving: Sieving is applied to separate mixtures that mostly contain substances of different sizes. The mixture is passed through the sieve pores. The smaller parts of the mixture pass through easily while retaining the larger parts of the mixture.
• Sedimentation: Sedimentation is a process in which the heavier impurities present in the liquid normally settle down at the bottom of the container containing the mixture. 
• Decantation: Decantation is a process for separating mixtures by removing a liquid layer free from precipitate or solids deposited from a solution. The aim may be to obtain a decent (liquid free of particulate matter) or recover precipitate.
• Filtration: Filtration is the most used method of separating a liquid from an insoluble solid. An excellent example of this is the mixture of sand in liquid. Filtration is used to eradicate solid particles from the liquid. A lot of filtering agents are commonly used as paper filters.
• Evaporation: Evaporation is a technique used to separate a mixture from a solvent and a soluble solid. The solution is heated until the organic solvent evaporates, where it turns into a gaseous state and mostly leaves the solid residue behind.
• Magnetic Separation: If one substance in the mixture possesses magnetic properties, this method is helpful. Strong magnets are used for the separation of magnetic elements.

In this chapter, we learned about mixtures and compounds. We talked about the various types of separation techniques used in mixtures and some key concepts like elements and compounds.

1. List some chemical methods used in separation?
   Distillation, membrane procedures, crystallisation, adsorption, absorption and oxidation are chemical methods used for separation and purification.
2. How can sand and salt be separated?
   It remains in the bath as sand or is applied to the tub or creates a film on the bottle’s bottom. As a result, sand doesn’t dissolve in water and is insoluble. It is easy to separate sand and water by separating the mixture. Salt may be segregated from a solution by evaporation.
3. What are the two kinds of mixtures?
   There are two kinds of mixtures: heterogeneous and homogeneous.
4. What is the difference between the compound, element and mixture?
   The compound contains atoms of different elements which are chemically combined in a fixed ratio. An element is a pure chemical substance of the same type of atom. Compounds contain various fixed-ratio elements organised in a given manner by chemical bonds. They only contain one type of molecule.
5. What are the similarities between the components and compounds?
   At the most basic level, both of them are made up of atoms.