Pure means substances without impurity but in science all things are mixture of so many substances  so they are not pure . Milk  consist of  water and fats .In science pure  substances are those in which all the elements have same chemical properties and made up of same kind of elements .

SUBSTANCE is a kind of matter that  cannot be separated into other kind of matter by any physical process  a pure substance are made of same element .

MIXTURE ; It is the substance in which two or  more substance (element / compound ) are simply mixed together in any proportion eg Air is a mixture of many gases

There are two types of mixture

a)Homogenous Mixture : It has no visible boundaries  of separation between the various  constituents  eg sugar in water it has a uniform  composition through out the mass .

b)Heterogenous Mixture : These types of mixtures have  visible boundaries of separation the various  constituents  eg  mixture of  sugar and sand  it does not have a unform  composition throughout  mass

SOLUTION : It is homogeneous mixture of solute and solvent. The component which is in small part is solute and the component in large amount is solvent .

Sugar + Water = solution  here sugar is solute and water is solvent .

Solutions are classified in three categories  a) True  solution in which the size of the particles  is less than 10 -9m , particles of solute  cannot be seen through naked eyes , they are Homogenous mixture  which cannot be separated by filtration ,they are transparent in nature, very much  stable do not settle down, they do not show Tyndall effect ,this type of solution diffuse rapidly through filter paper or parchment paper .  b) Colloidal Solution : In this kind of solution the size of solute particles  lies between  10-9 to 10-6 m , the particles of solute cannot be seen through the naked eyes , Itis  heterogenous  mixture ,cannot be separated by filtration, Translucent in nature  , stable in nature , shows tyndall effects , It passes through filter paper and cannot pass through  parchment paper  c) Suspension solution : Size of the solute particles is more than 10-6 m , particles can be seen through naked eyes ,Heterogenous mixture ,can be easily separated by filter paper ,Opaque in nature , unstable in nature , may or may not show tyndall effects ,They neither passes through filter /parchment paper .

SOME COMMON  COLLOIDS : Liquid / solid+ Gas  = Aerosol (Fog, Cloud , smoke )

Gas + Liquid = Foam  ( Shaving Cream ) ,   Liquid + Liquid = Emulsion ( Milk , Face Cream )       Solid+ Liquid =Sol (Mud , digene )  , Gas + Solid= Foam (rubber, sponge , Foam )                         Liq³uid + Solid =Gel (jelly , Cheese ) Note : gas in gas is not colloids

CONCENTRATION OF SOLUTION :  Mass by % mass =mass of solute x 100/ mass of solution

Mass by  % volume = Mass of  solute x100 /volume of solution


Evaporation : The basic principle out of the two components of mixture  one can evaporate which has low boiling point than the other having high melting point. In the mixture of dye ( higher bp) and water .Out of water and dye water evaporates  dye is left behind .

Centrifugation : The basic principle of the separation of substances or particles on the basis of their  density, when mixture is rotated very  fast the denser particles are forced at the bottom and  lighter particles remain on the surface eg used in diagnostic lab  for blood test and urine test , used in home /dairies  to separate butter from cream , Used  in washing machine dryers to squeeze out water from clothes

By Separating funnel : when two  immiscible liquids ( do not dissolve with each other) can be easily separated by this funnel . Let us suppose water and oil are mixed and put in the separating funnel  if we open the stop cock  first  water will be removed after than oil can be collected .In the same way extraction of iron ore takes place lighter slag is removed from molten  iron .

SUBLIMATION : Out of the two component one will sublimate and other is left behind In the mixture of NH4Cl and NaCl when it is heated NH4Cl being sublimate evaporates and NaCl is left some other sublimate are Camphor /naphthalene /anthracene/NH4Cl.

CHROMATOGRAPHY : the coloured component  of a mixture can be separated  by using  adsorbent on which they are absorbed  at different rates .( Surface absorption  is adsorption ) when water/any suitable solvent moves up the chromatography paper ink with two different colour separates because both colours are absorbed at different rates eg it is used  to separates colours of dyes /to separates pigments from natural colours like chlorophyll/separate drugs from blood

DISTILLATION : It is used to separate the miscible mixture liquids having different bp followed by condensation out of  two component one has lower bp and other have high  bp ,this process is used  for separating two or more miscible liquids ( see fig bk )

When  mixture of acetone and water is heated acetone having less bp boils  and moves to delivery tube within which it condenses back to liquid with the help of condenser clamped to it in this way acetone is separated water is left behind  distillation flask . We must use fractional distillation if there are more than two miscible liquids. Petroleum is separated into paraffin wax , lubricating oil , diesel , Kerosene ,petrol and petrol gas is separated by this method.

FRACTIONAL DISTILLATION OF AIR : Air is separated by this method  in which air is compressed and cooled with becomes liquid air than further allowed to warm up slowly in the fractional column and air is separated at different heights .

Important application a) In oil refineries to separate the crude oil into useful substances b) In is used for the separation of oxygen , liquid nitrogen  and argon from air.

CRYSTALLISATION : It is the method to remove the impurities from the mixture  by  first  dissolving in a suitable solvent and then crystallizing out the one component

Copper Sulphate crystals which are impure are  first dissolved in H2SO4 than heated to saturated solution.  This solution is left overnight so  only CuSO4  crystals on filter paper.

Crystallization is better than evaporation because some solids decomposes or charred upon heating to dryness during evaporation ( Sugar ),some impurities remain dissolved in solution after filtration. On the evaporation  these impurities do not evaporate and remain  with the mixture. It is used for the purification of salt from water , separation of crystal  from impure crystals ( alum ,copper sulphate )

WATER PURIFICATION IN WATER TREATMENT OF PLANT  : Reservoir  which contain  impure water  which transfer to sedimentation tank in which solid and heavy  particles settle down than further goes to loading tank  with the alum etc sedimentation of suspended impurities than it goes to filtration tank  where all impurities are filtered  after that it goes to chlorination tank  in which chlorine is added to kill germs after water is supplied to homes.

PHYSICAL CHANGES : It is  the change that are easily reversible ,no new products are formed and only change in state take place eg melting of ice.

CHEMICAL CHANGE: Itis the change that is not easily reversible  where  new product is formed ,often heat , light , sound or fizzing occurs ,and electricity may be produced such as wood burning .

ELEMENTS  are made of same type of atoms which are classified in metals, non metals and  metalloids.

METALS are the lustrous, malleable , ductile, sonorous , good conductor of heat and electricity eg gold iron

NON METAL  are the non lustrous, non malleable ,non ductile ,non sonorous , bad conductor of heat and electricity eg oxygen , phosphorous

METALLOIDS have intermediate properties between metals and non metals  eg boron , germanium ,silicon .

MIXTURE : Elements /Compounds are simply mixed so no new substance is formed , they do not combine in fix ratio, it shows the properties of its components , which can easily separated by mechanical method which is suitable  eg sugar in water , oil in water

COMPOUND  are the substances  which are reacted together with each other to make new substance ,the composition of of the component is fixed they combine together in a fixed ratio according to their masses , it does not show the properties of component elements  they can not be separated from each other by simple mechanical methods  such as water .




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