Ncert-notes-class-9-science-chapter2 Class 9 Notes | EduRev

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Class 9 : Ncert-notes-class-9-science-chapter2 Class 9 Notes | EduRev

 Page 1


18 
 
 
 
 
 
 
 
 
 
   
PURE SUBSTANCE MIXTURE 
? Pure   substance consists of a single 
type of substance . 
? Mixture consists of two or 
more pure substances. 
? Pure   substance cannot  be 
separated into other substances by 
physical methods. 
? Mixture can be separated into 
its components by physical 
methods. 
? Pure   substance  has its own 
definite properties. 
? Mixture   shows the 
properties of its components. 
 
Elements are made up of one kind of atoms only. Compounds are made up of one kind of 
molecules only. 
 
Difference between Compound &Mixture       
   [ refer NCERT text Book  Tab.2.2, page 26] 
 
Q.1   Is air around us a compound or mixture? 
Q.2   Water is a compound. Justify. 
Q.3   Classify the following as element , compound and mixture: Iron , sea water , Milk  
Q.4  Are the naturally occurring material in nature chemically pure substances? 
1. Pure Substance & mixture 
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Page 2


18 
 
 
 
 
 
 
 
 
 
   
PURE SUBSTANCE MIXTURE 
? Pure   substance consists of a single 
type of substance . 
? Mixture consists of two or 
more pure substances. 
? Pure   substance cannot  be 
separated into other substances by 
physical methods. 
? Mixture can be separated into 
its components by physical 
methods. 
? Pure   substance  has its own 
definite properties. 
? Mixture   shows the 
properties of its components. 
 
Elements are made up of one kind of atoms only. Compounds are made up of one kind of 
molecules only. 
 
Difference between Compound &Mixture       
   [ refer NCERT text Book  Tab.2.2, page 26] 
 
Q.1   Is air around us a compound or mixture? 
Q.2   Water is a compound. Justify. 
Q.3   Classify the following as element , compound and mixture: Iron , sea water , Milk  
Q.4  Are the naturally occurring material in nature chemically pure substances? 
1. Pure Substance & mixture 
www.ncerthelp.com
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 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
19 
 
 
 
 
2. Types of Mixtures 
Mixtures can also be grouped  
i) on the basis of their physical states: 
   SOLID  LIQUID  GAS 
 SOLID ? Salt and sugar ? Salt and water ? Dust in air 
 LIQUID ? Mercury and copper ? Alcohol and water ? Clouds 
 GAS ? Hydrogen and palladium ? Oxygen and water ? Air 
ii) on the basis of miscibility: 
Homogeneous Mixture  Heterogeneous Mixture  
? It consists of single phase. 
? Uniform composition.  
? Example:  Sugar dissolved in water 
? It consists of two or more phase. 
? Does not have uniform composition.  
? Example:  Air, sand and common salt. 
 
Q.1 Give one example for each of the following mixtures:  i) Solid/solid (homogeneous)            
        ii) Solid/solid (heterogeneous)   iii) Liquid/liquid (homogeneous)    iv) Liquid/liquid   
        (heterogeneous)     v) Gas/liquid (homogeneous).. 
Q.2  Classify the following as homogeneous & heterogeneous mixture: 
         i) sodium chloride & water   ii) glucose & water   iii) sand & water   iv) air 
 
4. Separating the components of a mixture 
    
  The components of a heterogeneous mixture can be separated by  
? simple methods like - 
                 hand picking , sieving , &  Winnowing   
?   special techniques  like - 
              i) Evaporation   :   a mixture of salt and water or sugar and water. 
            ii) Centrifugation  :  Butter from curd, Fine mud particles suspended in water. 
             iii) Decantation (Using separating funnel)  :  Oil from water. 
             iv) Sublimation :   Camphor from salt,  
             v) Chromatography  : Different pigments from an extract of flower petals. 
            vi) Distillation and fractional distillation  : Separating components of Petroleum 
          viii) Magnetic separation: Iron pins from sand. 
 
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 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
Page 3


18 
 
 
 
 
 
 
 
 
 
   
PURE SUBSTANCE MIXTURE 
? Pure   substance consists of a single 
type of substance . 
? Mixture consists of two or 
more pure substances. 
? Pure   substance cannot  be 
separated into other substances by 
physical methods. 
? Mixture can be separated into 
its components by physical 
methods. 
? Pure   substance  has its own 
definite properties. 
? Mixture   shows the 
properties of its components. 
 
Elements are made up of one kind of atoms only. Compounds are made up of one kind of 
molecules only. 
 
Difference between Compound &Mixture       
   [ refer NCERT text Book  Tab.2.2, page 26] 
 
Q.1   Is air around us a compound or mixture? 
Q.2   Water is a compound. Justify. 
Q.3   Classify the following as element , compound and mixture: Iron , sea water , Milk  
Q.4  Are the naturally occurring material in nature chemically pure substances? 
1. Pure Substance & mixture 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
19 
 
 
 
 
2. Types of Mixtures 
Mixtures can also be grouped  
i) on the basis of their physical states: 
   SOLID  LIQUID  GAS 
 SOLID ? Salt and sugar ? Salt and water ? Dust in air 
 LIQUID ? Mercury and copper ? Alcohol and water ? Clouds 
 GAS ? Hydrogen and palladium ? Oxygen and water ? Air 
ii) on the basis of miscibility: 
Homogeneous Mixture  Heterogeneous Mixture  
? It consists of single phase. 
? Uniform composition.  
? Example:  Sugar dissolved in water 
? It consists of two or more phase. 
? Does not have uniform composition.  
? Example:  Air, sand and common salt. 
 
Q.1 Give one example for each of the following mixtures:  i) Solid/solid (homogeneous)            
        ii) Solid/solid (heterogeneous)   iii) Liquid/liquid (homogeneous)    iv) Liquid/liquid   
        (heterogeneous)     v) Gas/liquid (homogeneous).. 
Q.2  Classify the following as homogeneous & heterogeneous mixture: 
         i) sodium chloride & water   ii) glucose & water   iii) sand & water   iv) air 
 
4. Separating the components of a mixture 
    
  The components of a heterogeneous mixture can be separated by  
? simple methods like - 
                 hand picking , sieving , &  Winnowing   
?   special techniques  like - 
              i) Evaporation   :   a mixture of salt and water or sugar and water. 
            ii) Centrifugation  :  Butter from curd, Fine mud particles suspended in water. 
             iii) Decantation (Using separating funnel)  :  Oil from water. 
             iv) Sublimation :   Camphor from salt,  
             v) Chromatography  : Different pigments from an extract of flower petals. 
            vi) Distillation and fractional distillation  : Separating components of Petroleum 
          viii) Magnetic separation: Iron pins from sand. 
 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
20 
 
 
 
Q.1  Name the process you would use to : 
         i) recover sugar from an aqueous sugar solution. 
        ii) separate mixture of salt solution and sand. 
Q.2  How will you separate a mixture of sand , water and mustard oil ?  
 
 
 
 
The amount of solute present in a given amount (mass or volume) of solution.  
                                                          Amount of solute                Amount of solute 
Concentration of a solution  =  _________________  OR  ____________________ 
                                                         Amount of solvent              Amount of solution 
  
The concentration of a solution can be expressed as mass by mass percentage or as mass by 
volume percentage. 
                                                                                 Mass of solute 
  Mass by mass percentage of a solution      = ------------------     x  100 
                                                                                Mass of solution 
                                                                                  Mass of solute  
 Mass by volume percentage of a solution   =   ------------------   x 100            
                                                                               Volume of solution 
 
Types of Solutions 
 
a) on the basis of size of solute particles: 
 
5. Concentration  of Solution 
True solution Sol [ Colloid] Suspension 
? Homogeneous  ? Heterogeneous  ? Heterogeneous 
? Size of solute 
particles is less than 
1 n m or 10
-9
 m . 
? Size of solute particles 
is between 1 nm to 
1000 nm. 
? Size of solute particles 
is more than 1000 nm. 
? Particles cannot pass 
through filter paper. 
? Particles can pass 
through filter paper. 
? Particles cannot pass 
thorough filter paper. 
? Stable ? Stable and settle only 
on centrifugation. 
? Unstable and settle 
down on its own.  
? Solution of sodium 
chloride in water, 
sugar & water. 
? Milk , Fog ? muddy water, chalk & 
water, 
? smoke in the air. 
www.ncerthelp.com
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 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
Page 4


18 
 
 
 
 
 
 
 
 
 
   
PURE SUBSTANCE MIXTURE 
? Pure   substance consists of a single 
type of substance . 
? Mixture consists of two or 
more pure substances. 
? Pure   substance cannot  be 
separated into other substances by 
physical methods. 
? Mixture can be separated into 
its components by physical 
methods. 
? Pure   substance  has its own 
definite properties. 
? Mixture   shows the 
properties of its components. 
 
Elements are made up of one kind of atoms only. Compounds are made up of one kind of 
molecules only. 
 
Difference between Compound &Mixture       
   [ refer NCERT text Book  Tab.2.2, page 26] 
 
Q.1   Is air around us a compound or mixture? 
Q.2   Water is a compound. Justify. 
Q.3   Classify the following as element , compound and mixture: Iron , sea water , Milk  
Q.4  Are the naturally occurring material in nature chemically pure substances? 
1. Pure Substance & mixture 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
19 
 
 
 
 
2. Types of Mixtures 
Mixtures can also be grouped  
i) on the basis of their physical states: 
   SOLID  LIQUID  GAS 
 SOLID ? Salt and sugar ? Salt and water ? Dust in air 
 LIQUID ? Mercury and copper ? Alcohol and water ? Clouds 
 GAS ? Hydrogen and palladium ? Oxygen and water ? Air 
ii) on the basis of miscibility: 
Homogeneous Mixture  Heterogeneous Mixture  
? It consists of single phase. 
? Uniform composition.  
? Example:  Sugar dissolved in water 
? It consists of two or more phase. 
? Does not have uniform composition.  
? Example:  Air, sand and common salt. 
 
Q.1 Give one example for each of the following mixtures:  i) Solid/solid (homogeneous)            
        ii) Solid/solid (heterogeneous)   iii) Liquid/liquid (homogeneous)    iv) Liquid/liquid   
        (heterogeneous)     v) Gas/liquid (homogeneous).. 
Q.2  Classify the following as homogeneous & heterogeneous mixture: 
         i) sodium chloride & water   ii) glucose & water   iii) sand & water   iv) air 
 
4. Separating the components of a mixture 
    
  The components of a heterogeneous mixture can be separated by  
? simple methods like - 
                 hand picking , sieving , &  Winnowing   
?   special techniques  like - 
              i) Evaporation   :   a mixture of salt and water or sugar and water. 
            ii) Centrifugation  :  Butter from curd, Fine mud particles suspended in water. 
             iii) Decantation (Using separating funnel)  :  Oil from water. 
             iv) Sublimation :   Camphor from salt,  
             v) Chromatography  : Different pigments from an extract of flower petals. 
            vi) Distillation and fractional distillation  : Separating components of Petroleum 
          viii) Magnetic separation: Iron pins from sand. 
 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
20 
 
 
 
Q.1  Name the process you would use to : 
         i) recover sugar from an aqueous sugar solution. 
        ii) separate mixture of salt solution and sand. 
Q.2  How will you separate a mixture of sand , water and mustard oil ?  
 
 
 
 
The amount of solute present in a given amount (mass or volume) of solution.  
                                                          Amount of solute                Amount of solute 
Concentration of a solution  =  _________________  OR  ____________________ 
                                                         Amount of solvent              Amount of solution 
  
The concentration of a solution can be expressed as mass by mass percentage or as mass by 
volume percentage. 
                                                                                 Mass of solute 
  Mass by mass percentage of a solution      = ------------------     x  100 
                                                                                Mass of solution 
                                                                                  Mass of solute  
 Mass by volume percentage of a solution   =   ------------------   x 100            
                                                                               Volume of solution 
 
Types of Solutions 
 
a) on the basis of size of solute particles: 
 
5. Concentration  of Solution 
True solution Sol [ Colloid] Suspension 
? Homogeneous  ? Heterogeneous  ? Heterogeneous 
? Size of solute 
particles is less than 
1 n m or 10
-9
 m . 
? Size of solute particles 
is between 1 nm to 
1000 nm. 
? Size of solute particles 
is more than 1000 nm. 
? Particles cannot pass 
through filter paper. 
? Particles can pass 
through filter paper. 
? Particles cannot pass 
thorough filter paper. 
? Stable ? Stable and settle only 
on centrifugation. 
? Unstable and settle 
down on its own.  
? Solution of sodium 
chloride in water, 
sugar & water. 
? Milk , Fog ? muddy water, chalk & 
water, 
? smoke in the air. 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
21 
 
 
 
[ types of colloids : refer NCERT Text Book  table 2.1 , page 18 ] 
Colloidal solution is a   heterogeneous mixture. It consists of two phases:- 
(i) Dispersed phase : component present in small proportion 
(ii) Dispersion medium : component present in large proportion 
The particles of colloid are large enough to scatter  a beam of light passing through it and 
make its  path visible. Thus, they show Tyndall effect. 
The colloidal particles are moving at random in a   zigzag motion in all directions. 
 This type of zig-zag motion of colloidal particles is  called Brownian movement. 
b) on the basis of amount of solute: 
Unsaturated solution Saturated Solution Supersaturated solution 
A solution which has lesser 
amount of solute that it can 
dissolve at a given temperature 
is known as unsaturated 
solution.  
A solution which has 
maximum amount of solute 
that it can dissolve at a given 
temperature is known as 
saturated solution. 
A solution which can dissolve 
amount of solute by increasing 
temperature saturated solution 
is known as supersaturated 
solution.    
 
c) on the basis of nature of solvent 
Aqueous solution Non-Aqueous solution 
The solution in which the solvent is water is 
known as aqueous solution. 
The solution in which the solvent is other 
than water (ether, alcohol or aceton) known 
as non-aqueous solution. 
 
 
Q.1 Classify the following substances into true solutions and colloidal solutions. 
         Milk , ink , starch dissolved in water. 
Q.2  A solution has been prepared by dissolving 5g of urea in 95 g of water. What is the mass   
       percent of urea in the solution? 
Q.3 Give an example of an aqueous solution in which gas is dissolved. 
 
 
6.Physical & Chemical Changes 
Physical changes -  Changes that do not result in the production of a new substance. 
? If you melt a block of ice, you still have H
2
O at the end of the  change. 
? If you break a bottle, you still have glass. 
www.ncerthelp.com
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 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
Page 5


18 
 
 
 
 
 
 
 
 
 
   
PURE SUBSTANCE MIXTURE 
? Pure   substance consists of a single 
type of substance . 
? Mixture consists of two or 
more pure substances. 
? Pure   substance cannot  be 
separated into other substances by 
physical methods. 
? Mixture can be separated into 
its components by physical 
methods. 
? Pure   substance  has its own 
definite properties. 
? Mixture   shows the 
properties of its components. 
 
Elements are made up of one kind of atoms only. Compounds are made up of one kind of 
molecules only. 
 
Difference between Compound &Mixture       
   [ refer NCERT text Book  Tab.2.2, page 26] 
 
Q.1   Is air around us a compound or mixture? 
Q.2   Water is a compound. Justify. 
Q.3   Classify the following as element , compound and mixture: Iron , sea water , Milk  
Q.4  Are the naturally occurring material in nature chemically pure substances? 
1. Pure Substance & mixture 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
19 
 
 
 
 
2. Types of Mixtures 
Mixtures can also be grouped  
i) on the basis of their physical states: 
   SOLID  LIQUID  GAS 
 SOLID ? Salt and sugar ? Salt and water ? Dust in air 
 LIQUID ? Mercury and copper ? Alcohol and water ? Clouds 
 GAS ? Hydrogen and palladium ? Oxygen and water ? Air 
ii) on the basis of miscibility: 
Homogeneous Mixture  Heterogeneous Mixture  
? It consists of single phase. 
? Uniform composition.  
? Example:  Sugar dissolved in water 
? It consists of two or more phase. 
? Does not have uniform composition.  
? Example:  Air, sand and common salt. 
 
Q.1 Give one example for each of the following mixtures:  i) Solid/solid (homogeneous)            
        ii) Solid/solid (heterogeneous)   iii) Liquid/liquid (homogeneous)    iv) Liquid/liquid   
        (heterogeneous)     v) Gas/liquid (homogeneous).. 
Q.2  Classify the following as homogeneous & heterogeneous mixture: 
         i) sodium chloride & water   ii) glucose & water   iii) sand & water   iv) air 
 
4. Separating the components of a mixture 
    
  The components of a heterogeneous mixture can be separated by  
? simple methods like - 
                 hand picking , sieving , &  Winnowing   
?   special techniques  like - 
              i) Evaporation   :   a mixture of salt and water or sugar and water. 
            ii) Centrifugation  :  Butter from curd, Fine mud particles suspended in water. 
             iii) Decantation (Using separating funnel)  :  Oil from water. 
             iv) Sublimation :   Camphor from salt,  
             v) Chromatography  : Different pigments from an extract of flower petals. 
            vi) Distillation and fractional distillation  : Separating components of Petroleum 
          viii) Magnetic separation: Iron pins from sand. 
 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
20 
 
 
 
Q.1  Name the process you would use to : 
         i) recover sugar from an aqueous sugar solution. 
        ii) separate mixture of salt solution and sand. 
Q.2  How will you separate a mixture of sand , water and mustard oil ?  
 
 
 
 
The amount of solute present in a given amount (mass or volume) of solution.  
                                                          Amount of solute                Amount of solute 
Concentration of a solution  =  _________________  OR  ____________________ 
                                                         Amount of solvent              Amount of solution 
  
The concentration of a solution can be expressed as mass by mass percentage or as mass by 
volume percentage. 
                                                                                 Mass of solute 
  Mass by mass percentage of a solution      = ------------------     x  100 
                                                                                Mass of solution 
                                                                                  Mass of solute  
 Mass by volume percentage of a solution   =   ------------------   x 100            
                                                                               Volume of solution 
 
Types of Solutions 
 
a) on the basis of size of solute particles: 
 
5. Concentration  of Solution 
True solution Sol [ Colloid] Suspension 
? Homogeneous  ? Heterogeneous  ? Heterogeneous 
? Size of solute 
particles is less than 
1 n m or 10
-9
 m . 
? Size of solute particles 
is between 1 nm to 
1000 nm. 
? Size of solute particles 
is more than 1000 nm. 
? Particles cannot pass 
through filter paper. 
? Particles can pass 
through filter paper. 
? Particles cannot pass 
thorough filter paper. 
? Stable ? Stable and settle only 
on centrifugation. 
? Unstable and settle 
down on its own.  
? Solution of sodium 
chloride in water, 
sugar & water. 
? Milk , Fog ? muddy water, chalk & 
water, 
? smoke in the air. 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
21 
 
 
 
[ types of colloids : refer NCERT Text Book  table 2.1 , page 18 ] 
Colloidal solution is a   heterogeneous mixture. It consists of two phases:- 
(i) Dispersed phase : component present in small proportion 
(ii) Dispersion medium : component present in large proportion 
The particles of colloid are large enough to scatter  a beam of light passing through it and 
make its  path visible. Thus, they show Tyndall effect. 
The colloidal particles are moving at random in a   zigzag motion in all directions. 
 This type of zig-zag motion of colloidal particles is  called Brownian movement. 
b) on the basis of amount of solute: 
Unsaturated solution Saturated Solution Supersaturated solution 
A solution which has lesser 
amount of solute that it can 
dissolve at a given temperature 
is known as unsaturated 
solution.  
A solution which has 
maximum amount of solute 
that it can dissolve at a given 
temperature is known as 
saturated solution. 
A solution which can dissolve 
amount of solute by increasing 
temperature saturated solution 
is known as supersaturated 
solution.    
 
c) on the basis of nature of solvent 
Aqueous solution Non-Aqueous solution 
The solution in which the solvent is water is 
known as aqueous solution. 
The solution in which the solvent is other 
than water (ether, alcohol or aceton) known 
as non-aqueous solution. 
 
 
Q.1 Classify the following substances into true solutions and colloidal solutions. 
         Milk , ink , starch dissolved in water. 
Q.2  A solution has been prepared by dissolving 5g of urea in 95 g of water. What is the mass   
       percent of urea in the solution? 
Q.3 Give an example of an aqueous solution in which gas is dissolved. 
 
 
6.Physical & Chemical Changes 
Physical changes -  Changes that do not result in the production of a new substance. 
? If you melt a block of ice, you still have H
2
O at the end of the  change. 
? If you break a bottle, you still have glass. 
www.ncerthelp.com
Visit www.ncerthelp.com for Ncert Solutions in Text and Video , CBSE Sample papers, Exam tips,
 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
22 
 
 
 
Examples  :  melting, freezing, condensing, breaking, crushing, cutting, and bending. 
 
Chemical changes - Changes that result in the production of another substance. 
? As in the case of autumn leaves, a change in color is a clue to indicate a chemical 
change.  
? a half eaten apple that turns brown.  
  
Q.1   Which of the following is an example of physical change?  
         a. Mixing baking soda and vinegar together, and this causes bubbles and  foam.  
          b. A glass cup falls from the counter and shatters on the ground.  
         c. Lighting a piece of paper on fire and the paper burns up and leaves ashes.  
        d. Baking a birthday cake for your mother.  
Q.2. Which of the following is an example of chemical change?  
         a. Filling up a balloon with hot air.  
         b. Taking a glass of water and freezing it by placing it in the freezer.  
         c. A plant collecting sunlight and turning it into food.  
        d. Your dog ripping up your homework.  
3. Which change can be easily be reversed?  
         a. Chemical Change  
         b. Physical Change  
         c. Both a physical and chemical change  
        d. Neither a physical or chemical change  
 
 
7.Alloys 
 
       A material that has metallic properties and is composed of two or more chemical    
        elements of which at least one is a metal . 
? These cannot be separated into their components by physical methods. 
? However, these are considered as mixture   because these show the properties of its 
constituents and can have variable composition. 
The benefit of alloys is that you can combine metals that have varying characteristics to 
create an end product that is stronger, more flexible, or otherwise desirable to 
manufacturers.  
 
? Aluminium alloys are extensively used in the production of automotive engine 
parts. 
? Copper alloys have excellent electrical and thermal performance, good corrosion 
resistance, high ductility and relatively low cost. 
 
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 NCERT BOOKS, Motivational Videos, Notes for All Classes and Many More... 
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