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IS MATTER AROUND US PURE

 A mixture contains more than one substance (element and/or compound) mixed in any proportion.

 Mixtures can be separated into pure substances using appropriate separation techniques.

 A solution is a homogeneous mixture of two or more substances. The major component of a solution is called the solvent, and the minor, the solute.

 The concentration of a solution is the amount of solute present per unit volume or per unit mass of the solution/solvent.

 Materials that are insoluble in a solvent and have particles that are visible to naked eyes, form a suspension.

 A suspension is a heterogeneous mixture.

Colloids

 are heterogeneous mixtures in which the particle size is too small to be seen with the naked eye, but is big enough to scatter light.

 useful in industry and daily life.

 The particles are called the dispersed phase and the medium in which they are distributed is called the dispersion medium.

 Pure substances can be elements or compounds.

 An element is a form of matter that cannot be broken down by chemical reactions into simpler substances.

 A compound is a substance composed of two or more different types of elements, chemically combined in a fixed proportion.

 Properties of a compound are different from its constituent elements, whereas a mixture shows the properties of its constituting elements or compounds.

 Mixtures are constituted by more than one kind of pure form of matter, known as a substance.

 A substance cannot be separated into other kinds of matter by any physical process which contains more than one substance.

 mixture which has a uniform composition throughout. Such mixtures are called homogeneous mixtures or solutions.

 Some other examples of such mixtures are: 

(i) salt in water and (ii) sugar in water.

 a homogeneous mixture can have a variable composition.

 mixtures, which contain physically distinct parts and have non-uniform compositions.

 Such mixtures are called heterogeneous mixtures.

 Mixtures of sodium chloride and iron filings, salt and sulphur, and oil and water are examples of heterogeneous mixtures.

Alloys:

 homogeneous mixtures of metals and cannot be separated into their components by physical methods.

 considered as a mixture because it shows the properties of its constituents and can have variable composition.

 For example, brass is a mixture of approximately 30% zinc and 70% copper.

 A solution has a solvent and a solute as its components.

Properties of a solution

 A solution is a homogeneous mixture.

 The particles of a solution are smaller than 1 nm (10 -9 metre) in diameter.

 Cannot be seen by naked eyes.

 Because of very small particle size, they do not scatter a beam of light passing through the solution.

 The path of light is not visible in a solution.

The solute particles

 Cannot be separated from the mixture by the process of filtration.

 do not settle down when left undisturbed, that is, a solution is stable.

 when no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

 The amount of the solute present in the saturated solution at this temperature is called its solubility.

 If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.

 A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.

 Particles of a suspension are visible to the naked eye.

Properties of a Suspension

 Suspension is a heterogeneous mixture.

 The particles of a suspension can be seen by the naked eye.

 The particles of a suspension scatter a beam of light passing through it and make its path visible.

 The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable.

 They can be separated from the mixture by the process of filtration. a colloidal solution is a heterogeneous mixture, for example, milk.

Properties of a colloid

 A colloid is a heterogeneous mixture.

 The size of particles of a colloid is too small to be individually seen by naked eyes.

 Colloids are big enough to scatter a beam of light passing through it and make its path visible.

 They do not settle down when left undisturbed, that is, a colloid is quite stable.

 They cannot be separated from the mixture by the process of filtration.

 But, a special technique of separation known as centrifugation can be used to separate the colloidal particles.

 Some examples of solids which sublime are ammonium chloride, camphor, naphthalene and anthracene. process of separation of components of a mixture is known as chromatography.

 Chromatography is the technique used for separation of those solutes that dissolve in the same solvent.

Applications

 To separate • colours in a dye • pigments from natural colours • drugs from blood. distillation.

 It is used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.

 The crystallisation method is used to purify solids.

 Crystallisation technique is better than simple evaporation technique as –

 Some solids decompose or some, like sugar, may get charred on heating to dryness.

 Some impurities may remain dissolved in the solution even after filtration.

 On evaporation these contaminate the solid.

 The properties that can be observed and specified like colour, hardness, rigidity, fluidity, density, melting point, boiling point etc. are the physical properites.

Also read :Our Environment

Pure Substances Elements

 Element as a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

 Divided into metals, non-metals and metalloids.

 show some or all of the following properties:

 Have a luster (shine).

 have silvery-grey or golden-yellow colour.

 conduct heat and electricity.

 are ductile (can be drawn into wires).

 are malleable (can be hammered into thin sheets).

 are sonorous (make a ringing sound when hit).

 Mercury is the only metal that is liquid at room temperature.

 Non-metals usually show some or all of the following properties:

 They display a variety of colours.

 They are poor conductors of heat and electricity.

 They are not lustrous, sonorous or malleable.

 Examples of non-metals are hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine etc.

 A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

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