Revision: Science >> Separation of Substances Science Secondary School (English Medium) (5 to 8) Class 6 CBSE

Immiscible liquids : Heterogeneous liquid-liquid mixtures are called immiscible liquids.

Alloy: “A homogeneous solid mixture of two or more metals or a metal and a non-metal is called an alloy.”

Mixtures are formed when two or more substances are mixed together without participating in a chemical change. A mixture has a variable composition. A mixture shows the properties of the constituent substances. Physical methods can easily separate the constituents.

• Atoms/molecules of a mixture are of two or more types.
• The constituent molecules of a mixture are different from each other and are not joined by chemical bonds.
• Components in a mixture retain their original properties because they are not chemically combined.
• The proportion of constituent substances in a mixture can change.
• The properties of constituent substances are retained in the mixture. 
• Unlike compounds, mixtures do not have a fixed ratio of their components.

For Examples,

Air is a mixture containing nitrogen (N₂), oxygen (O₂), and other gases.

Types of mixture

1. Homogeneous Mixtures: Homo means same. A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture. For example, salt in water. It has a uniform composition, and it can’t be separated out physically.
2. Heterogeneous Mixture: Hetero means different. A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. For example, vegetable soup. It has a non-uniform composition and can be separated out physically.

Pure substance: “Pure Substance is either element or compound. It contains the same kind of atom or molecules and has a definite set of physical and chemical properties.”

Impure substance: “A substance in which some other substances are also present in smaller or larger amounts is called an impure substance. Mixtures are impure substances. An example of an impure substance is air.

Solution: “The homogeneous mixture of water (or any other solvent) and a substance soluble in it is called a solution.”

Heterogeneous mixture: “A mixture in which the components are not uniformly distributed through its volume and can be easily seen separately is called a heterogeneous mixture.”

Homogeneous mixture: “A mixture in which its constituents are uniformly distributed throughout its volume and cannot be seen separately is called a homogenous mixture.”

Miscible liquids : Homogeneous liquid-liquid mixtures are called miscible liquids.

Evaporation: Evaporation is a process which is used to separate a solid substance dissolved in liquid. It is based on the fact that liquids vaporize easily whereas solids do not.

Evaporation Is the process of converting a liquid into its vapour state either by exposing it to air or by heating.

Evaporation : Is the process ~of converting a liquid into its vapours state either by exposing it to air or by heating.

The process in which liquid is converted into its vapor phase at its boiling point and the vapor is then condensed back to liquid on cooling is known as distillation.

Distillation : Distillation is the method of getting a pure liquid from a solution by evaporating and then condensing the vapours.

A homogeneous mixture of two or more substances, whose relative amounts may be changed within certain limits, is called a solution.

A solvent is a medium in which a solute dissolves. It is in large quantity in a solution. Water is the most common solvent. The other solvents are alcohol, carbon tetrachloride, etc.

Example: Water

A homogenous mixture of a solute in a solvent is called a solution.

The substance which dissolves or disappears in the solvent, i.e., liquid, to form a solution is called a solute. E.g., sodium chloride.

A solute is a substance that dissolves in a medium, which can be water or any other substance. A solute is in a smaller quantity in a solution. e.g., sodium chloride.

It is characterised as a solution that adheres to Raoult's Law, with no interactions between the molecules and no volume or heat change during mixing.

For an ideal solution, Enthalpy of mixing of the pure components to form the solution is Δ_mix H = 0 and the volume of mixing is Δ_mix V = 0.

Two or more solutions exerting the same osmotic pressure are called isotonic solutions.

When two solutions are separated by a semipermeable membrane and no osmosis occurs, i.e., there is no net flow of water on either side through the membrane, the solutions are said to be isotonic solutions. If the membrane is perfectly semipermeable, the two solutions possess the same osmotic pressure and are also referred to as iso-osmotic solutions.