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Examples of Miscible Liquids

We know that all matter can exist in three possible states which are different from each other in their arraignment of particles. Solid states are compact with a regular arrangement of particles whereas liquid particles have more kinetic energy compare to gaseous state. The properties of liquid state are almost intermediate of solid and gaseous state. Two liquids can show different chemical and physical properties.

On the basis of their properties, liquids can be separated from their mixtures. There are several methods for the separation of liquids from their mixtures. For example fractional distillation is used to separate liquids on the basis of their boiling points whereas chromatography is used to separate coloured compounds. The mixtures of liquids can be classified in two types; miscible and immiscible. Immiscible liquids form two separate layers and cannot mix with each other.

In such mixtures, the attraction force between the molecules of same liquid is too strong and requires a large amount of energy which cannot be released by when the two liquids mix. The polarity in liquids determines their mixing tendency with other liquids.
A polar molecule has two ends, positive and negative end attract the opposite ends to form strong inter-molecular bonds. On the contrary, non-polar liquids have weak van der Waals forces of attraction between them. Liquids of same polarities are mixed together to form miscible liquids such as mixture of alcohol with water are an example of miscible liquid. But molecules with low polarity cannot mix together and form immiscible liquids. For example oil and water don't mix with each other and form two separate layers with each other. But pouring alcohol into water forms a single liquid phase with not meniscus between both liquids. Some liquids are partially miscible with each other such as mixture of butanol in water.

Another example of miscible liquids is the mixture of di-chlormethane and chloroform or milk and water.  It is difficult to separate two miscible liquids by simple physical methods. Usually fractional distillation is used to separate miscible liquids as they have different boiling points.

Oil and water is the classic example of immiscible liquids. Since water is a polar molecule with one positive and negative ends, but oil is a non-polar molecule with long hydrocarbon chain. Therefore both cannot mix with each other to form a mixed phase. Similarly the mixture of pentane and acetic acid is an example of immiscible liquids.  The mixing of molten silver and lead is used to separate silver form lead in Parkinson’s method.

The mixture of iron sulphides and silicates in magma is an immiscible liquid. Both of these compounds; FeS and silicate do not mix due to less Gibbs free energy of minerals compare to the Gibbs free energy of mixing. All polar liquids are miscible with each other and miscible in water as well. Water acts as a good solvent for all the polar liquids. Miscibility of liquids makes homogenous mixtures. Same term can also be used for solid and gaseous states.