Is Matter Around Us Pure 314a

Is Matter Around Us Pure?

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Science I

Std IX

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Introduction  For a common person pure means

having no adulteration. He expects salt,ghee,milk to be pure.  For a scientist all above things are actually mixtures of different substances. For him something is pure when all the constituent particles of that substance are the same in their chemical nature. Science I

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Mixture and Substance Mixtures are constituted by more than one kind of pure form of matter called as a substance.  A substance can not be separated into other kinds of matter by any physical process.  Milk is a mixture of water, fat and proteins.  Sugar is a substance since it contains only one kind of pure matter and its composition is the same throughout. 

Science I

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Types of Mixtures Homogeneous mixtures or solutions. E.G.: Copper sulphate solution. It has uniform composition.  Heterogeneous mixtures. Non-uniform composition. E.G. Soil, oil and water. 

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Types of Mixtures Mixture of copper sulphate and water

Particles are not visible. Path of light beam not visible. Components can not be separated by filtration

Solution

Mixture of wheat flour and water

Particles are visible. Path of light beam visible. Components can be separated by filtration

Suspension

Mixture of milk and water

Particles are not visible. Path of light beam visible. Components can not be separated by filtration

Colloidal solution

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What Is a Solution ? 

A solution is a homogeneous mixture of two or more substances.

Solution Type Example 1 Gas in gas Air 2 Gas in liquid Aerated water(Soda) 3 Liquid in liquid Lemon juice and water,water and alcohol 4 Solid in liquid

Sea water, sugar solution

5 Solid in solid

Alloys of metals Science I

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Properties of a Solution A solution is homogeneous mixture. Particles are smaller than 10 nm.  Because the particle size is too small,they do not scatter beam of light ing through the solution.  The solute particles can not be separated from the solution by the process of filtration or sedimentation.Solution is stable. 

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Concentration of Solution Mass by mass percentage of a solution = Mass of solute x 100 Mass of solution Mass by volume percentage of a solution = Mass of solute Volume of solution x100 Science I

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What Is a Suspension ? 

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

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Properties of a Suspension A suspension is a heterogeneous mixture.  Particles of suspension can be seen by naked eyes.  They scatter a beam of light ing through it and make the path of light visible.  The solute particles settle down on standing. This means a suspension is unstable.Solute can be separated by sedimentation or filtration. 

Science I

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What Is a Colloidal Solution ? 



The particles of a colloid are uniformly spread throughout the solution. Due to relatively smaller size of the particles,as compared to that of a suspension,the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture. E.G. Milk. Solute particles of a colloidal solution scatter a beam of light. This effect is known as Tyndall effect. Science I

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Properties of a Colloidal Solution A colloid is 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 ing through it and make its path visible.  Constituents of a colloid can not be separated by process of filtration. Technique of centrifugation needs to be used for this. 

Science I

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Components of a Colloidal Solution The dispersed phase and the dispersed medium are the two components of a colloid.  The solute like component or the dispersed particles in a colloid form its dispersed phase.  The component in which the dispersed phase is suspended is known as the dispersing medium. 

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Examples of Colloids Dispersed phase

Dispersing Type medium

Example.

Liquid Solid

Gas Gas

Aerosol Aerosol

Fog, clouds, mist Smoke, automobile exhaust

Gas Liquid

Liquid Liquid

Foam Shaving cream Emulsion Milk, face cream

Solid Gas

Liquid Solid

Sol Foam

Milk of magnesia, mud Foam, rubber, sponge,pumice.

Liquid Solid

Solid Solid

Gel Solid sol

Jelly,cheese,butter. Coloured gemstone,milky glass.

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Separating the Components of a Mixture. Heterogeneous mixtures : hand picking , sieving , filtration.  Dye from ink : evaporation , paper chromatography.  Cream from milk : centrifugation.  Two immiscible liquids : formation of layers due to difference in densities. Layers are then separated.  Sublimating solids in a mixture are separated by sublimation.  Miscible liquids: fractional distillation. 

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Separating the Components of a Mixture. Gases from air : initial compression and refrigeration liquefies the air. Liquid air is allowed to warm up gradually in a fractional distillation columns separate one by one at their boiling points.  Crystalline substances : crystallisation. E.G. Salt. 

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Physical and Chemical Changes Physical change : the inter conversion of states is physical change. There is no change in composition of the substance. There is no chemical change.E.G. Ice, water, steam,water vapour are chemically the same.  Chemical change: when one substance reacts with another to create a resultant substance / s with different chemical properties. E.g. burning of oil. 

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Types of Pure Substances Elements : A basic form of matter that can not be broken down into simpler substances by chemical reaction.  Compounds : A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion. 

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Types of Elements METALS

NON-METALS •Have variety of colours.

• Have luster (Shine). • Have silvery-grey or goldenyellow color.

•Poor conductors of heat and electricity.

• Conduct heat and electricity.

•Non lustrous, sonorous and malleable.

• Are ductile.

•E.g. Hydrogen, Oxygen,Carbon

• Are malleable.

METALLOIDS

• Are sonorous. •E.g.:Gold,silver,copper,iron, mercury(liquid). Science I

•Intermediate metallic and nonmetallic properties •E.g. Boron, silicon, germanium Std IX

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Mixtures and Compounds Mixtures

Compounds

1 Elements or compounds just

Elements react to form a new compound.

2 A mixture has a variable

The composition of each new substance is always fixed.

mix together to form a mixture and no new compound is formed. composition

3 A mixture shows the properties The new substance has totally new of the constituent substances.

4 The constituents can be

separated fairly easily by physical methods. Science I

properties.

The constituents can be separated only by chemical or electrochemical reactions. Std IX

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Is Matter Around Us Pure?

End Slide

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